sorry for my poor spelling well, typing in that post above....... my hands don't work like they should to much these days
another thing about your TOP national Brands like Trane, Carrier, Amana, etc.... is they all offer some pretty significant Manufactuers Rebates of $500 up to $1,500+ off of their complete systems..... most times these come as either straight off the top of the said price or you can actually get a check mailed back to you from the Manufactuer of the equipment......
if you are not ffered anything like this, ask. and ask if the HVAC Company is an Official "HVAC Brand Name" Equipment Dealer..... almost anyone can get/sell Trane now that HomeDepot has started offering Trane....... also, American Standard is the exact same thing as Trane ( they use to Own Trane brand....... look on any Trane equipment tag , it would say American Standard coproration / The Trane Company ........
sometimes you can get American Standard cheaper than Trane in certian areas..... and still get the same types of warranty, performance, rebates etc....
Carrier and Bryant are the same as well, just different colors of the equipment
Rheem, Rudd, Corsair, WeatherKing are all the same people/equipment
just to give you some more knowledge......
I have installed them all..... I would prefer 1st American Standard or Trane brand, 2nd would be Carrier, 3rd would be Amana, anything after that they all about the same....... amana's 16 SEER and up systems were offering lifetime warranty / equipment replacement on their systems not long ago. but I have been disabled since Sept 2009. so I just kind of keep up with the HVAC News sporadically now a days......
good luck