Greetings all. Thanks, in advance, for your help.

Been following for a while and will try to post all relevant info but i'm sure I'll miss something so ask away.

I'm the homeowner and getting ready to contract a full system replacement of several 15-year old rheem systems. Home is in Texas, built in late nineties. We've done a load calc and feel good about the tonnage, SEER, AFUE, etc. The ducts from the plenum to the vents will be checked and replaced as necessary. We're plugging in a few additional returns and reassigning a few supplies. So, the guts are good.

Furnaces are in the attic and horizontal.

What I need is to confirm or poke holes in the equipment list...here it is:

5 ton
TUD2C100ACV52A furnace
4TXFH063C23 coil
4TTZ0060 condenser
TCONT900 stat
Aprilaire 5000 filtration

4 ton
TUD2C08CC3 furnace
4TXCC008CC3 coil
4TTZ0048 condenser
TCONT900 stat
Aprilaire 5000 filtration

Questions:
1. Why didn't the contractor select the TUD2C080ACV42A for the 4 ton furnace?
2. Is the TCONT900 a good choice or should we consider one of the Honeywell IAQ units?

Thanks again.