There is a metric asston of professional members here from Texas.
I would say your best bet would be to find one of them that will help you out.
Yes, installation is the most important factor. Sizing and duct design also play a big role. As far as brand, go with what your contractor provides. So basically, don't buy the system, but the contractor......
Your best bet is to find a member of this site from your area. Because it has been discussed before. And only the true professionals that strive to become better are a part of this forum. You get hooked up with one of us, and your almost guarenteed to get exactly what you are looking for. Especially with the rest of us checking up on you.
I fully support the military and the War on Terrorism.
If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.
If you do know, then do. But do it right. Otherwise, you may not be doing it long.