What wind system would you recommend...

You did not provide enough information for me to make any recommendation.

Is this a grid only system, grid with battery backup, or off grid ?  Are you thinkiing wind only, or wind and solar ? How large of an electric load are you trying to support ?
What is the average wind speed at your site ? is that a measured speed or an estimate ?
Do you have any part of an alternative energy system installed? If so, what ? Or a you just starting to think about it ?

The more you can tell us, the better replies will be.

�I'm hoping our energy will go down even more with new windows, insulation, siding, doors, and geothermal unit.�

I like the energy conservation measures and would encourage you to complete the ones that will impact your electric usage (or at least have strong firm estimates of their impacts), before making final sizing decisions on your alternative energy system.  My experience is that conservation is almost always cheaper than generation.  Also, take a look at your well pump.  If it is say 10 years old or more, a new model might be more efficient. A well is also a prime candidate for a small stand-alone wind or solar application. Even if you just off load 80 percent of your pumping needs onto an alternative system, it can dramatically reduce electric bill. It can also give you experience with an alternative energy system on your site, and that data will help with sizing a big system. Also, look at insulating the hot water heater and all the hot water lines, if they are not already done. It�s a good idea no matter what you are using, but if you have electric hot water, it will also help reduce the total electric bill/generation need.

I also like your grid tie only approach, as it eliminates the need for batteries. Other sites may need them, but if you can get along without them, it reduces the cost and hassles.

�At this time, I'm thinking wind only and not solar due to economics and location.�

For most locations, solar is generally cheaper than wind. So, you either have an exceptional wind location, a very bad solar location, or some of the assumptions made in your economics may be in-correct.    I am not saying that they are wrong, just suggesting that you double-check all of your assumptions.

�The average wind speed at according to the Wisconsin Department of Administration Energy Division our location has an average wind speed of 15 - 15.5 mph.�

The 15-16mph range first shows up on the 100 meter map. That is 100 meters (328 feet) above ground level.  Hills and ridges can put you up near that height, so that you can SOMETIMES get into those wind speeds with a much shorter tower. However, many times the wind at lower levels hits the hill or ridge and starts pushing the various levels upwards. So, even on top of the ridge, you still might need a real tall tower, to reach those wind speeds.

If you have anything close to the 15mph speed near ground level, the trees on your property (and particularly those near the best potential sites) should show signs of �flagging�. The up wind branches will be shorter than the downwind branches and may be turning slightly upwards. The downwind branches will be longer, and most of the "side branch" branches will be laying closer to the main branch, as compared to the upwind side.  If you can not see some evidence of flagging, I would really question the wind speed.  

Another sign you can look for, is the existence of other wind turbines (not the old fashioned wind mill pumps) in your general vicinity. If there are not any within 5-10 miles of you, it could be an indication that the area is not really suitable. If you do see them, I would try to make contact with one or more of the owners and ask them about the machines. Have they met their expectations, were there any surprises, etc.  While their experience may not be specific to your site, it at least gives you a local baseline. You may also learn who are �the good dealers� and the �not so good dealers� in your local area.

�Currently our average household energy usage is about a 900 to 1100 Kwts per month.�

From the 900-1100 kWh (kilowatt hours) per month and the interest in the 3kW machines, I am assuming that you are trying to reduce your bill to near zero. If your property happens to have 3 good windmill sites, I would give some consideration to using three 1 kw machines. First they are smaller and lighter than the 3kw class, which puts them into a job that can be done by a handy (perhaps very handy)homeowner. (The 3kW class often is a job for professionals, and often requires cranes or specialized equipment.) It is a lot easer to raise and lower the 1kW class. I particularly like the tilt up tower designs that can be used with them. The machines can be lowered to the ground for maintenance, vs trying to work on them in the air.  I have seen more people hurt by slips, falls, and dropped objects around towers, than by other incidents. So, I would avoid having to climb the tower at all cost. Remember that you need to pull maintenance at least once a year, and unfortunately, sometimes more often.  

Multiple small machines open up other options. You could install one and run it for a year to get some real performance numbers on your property, and then decide whether or not to install the additional capacity.  With the 3 kW, you do it all at once, and then if it doesn�t meet expectations, you stuck with the large investment and lower than expected returns. You have no chance to limit any losses, or change your mind.
With the 1 kw, you would have the chance to review it. If (for example) you expected 300kwh and only average 225kwh, you can make the decision to stop there. Or, you would know that with the additional two would make about 675kwh, and you can re-evaluate the additional cost based upon that knowledge.  Or if you had bought a shorter tower on the first one, the real data might convince you invest a little more money and go with taller towers for #2 and #3. (actually, I believe in buying the tallest production tower you can get for a specific wind mill. It will generally be the most cost effective in the long run)  

With three machines, you always have at least two running, even if you take one down for maintenance or repairs.  If you are stuck waiting for a part, you are still reducing the bill by 2/3s.  With one big machine its running or it is not.
Depending on where you buy the machines and the exact installation costs, you can often install three of the 1kw for the same dollars as a single 3kw machine.

Also, the available stock towers for 1 kw class machines tend to be taller than those for the heavier 3 kw class.  Three 1 kw machines at 100 feet will normally out perform one 3 kw machine at 70 feet, even when located on the same ridgeline.  

Wisconsin�s �focus on energy program� will pay 75 percent of the cost of a site assessment for approved home owners. A site assessment runs about  300-400 dollars in most areas. They generally look at all sources of alternative energy for the site, even though the request is for �wind�.  It is money well spent at the full cost, and an even greater bargain if you only have to pay for � of it).  The info and application form are at
http://www.focusonenergy.com/portal.jsp?pageId=11

The other thing I would look for (and the site assessment should too) is for a mini hydro possibility. A small mini hydro say 400 watts (that is watts (W), not kilowatts (kW).) can produce about 288 kilowatt hours a month because it is running 24/7.  If we compared it to a Bergy XL-1 (a 1 kilowatt machine), Bergy estimates about 275 kwh/month when installed on a 30 foot tower in a 15 mph wind speed.  The lesson of this example is to look at the monthly (or yearly) production estimates when comparing the installed cost (cost per kilowatt hours per month/year installed) of a system, not the cost per kilowatt of generation installed. (Even in comparing wind turbines against each other use the kwh/month figures, some wind tubine supplies use an unrealistic kilowatt rating)

I hope you find the above info useful, even though it may not directly answer the question(s) you had in mind when you asked. The Alt-E University (tab near top of page) has some excellent info on wind, solar and hydro. I would suggest that you might want to spend some time going thru it, if you haven�t already done so.  For further wind info, try Paul Gipe�s site.  
http://www.wind-works.org/
And I recommend his books, particularly Wind Energy Basics, highly. It might be available at your library, but is well worth buying, even at full retail.

Feel free to ask additional questions, or for clarification on anything I said.

Oso

I think it was in a movie, a phrase that was used "just because we can do a thing, doesnt automatically mean we should do that thing." I think it was Jurrasic Park.
The utilization of electricity as we know it today is only 100 years old give or take a decade.
No matter what ones religion is or isn't, none of us can deny that humans have lived on this Earth for at least 7,000 years without the utilization of electricity as we know it today.

Ask yourself "do I really need all of this electricity I am using to live on the planet Earth?"