I'm a newbie here so give me a little leash on my request. I know enough to be dangerous about HVAC. I am currently in the process of working on finishing out my 2nd floor attic which is adjacent to my game room which is finished and separated by an insulated exterior door. I currently have an 8 yr old 1.5 ton Trane electric heat pump servicing roughly 750 finished sq ft upstairs. My addition will add approx 8-900 sq ft upstairs. Obviously my current setup will not service that. I have had a trane contractor come out and quote me a 3 ton, 13,15 and 18 seer option. I just had a different contractor out this morning that essentially eyeballed it and said I think we'll need to add one return and we can do a 3 ton to cover it, he recommended a 13 or 15 Seer American Standard unit. I would love to do a gas furnace option if possible but I'm on LP for now and hope that natural gas will make it out to me in the near future. I am in NC and we do have quite a few weeks every summer with 100 degree and 60-80 percent humidity days. That current 1.5 ton would let it get up to 78 or 80 on really hot days as it just can't keep up.

I guess what I need help with is how do I know the differences in these various brands and types of units? Also, if I am doing a dedicated theater for most of this space I am finishing and I plan on also having an equipment room that will get very hot and a separate bedroom, will one return cut it? I would think I would need at least two to move enough air. The tech this morning said oh well we'll just do one bigger one in the theater. I didn't really like that answer.

Looking for help, glad I found this place!