I've just moved into my new 1600 s.f. home with a Rheem RGPN 05eauer gas furnace. I had the unit prewired for a/c and the hvac contractor installed a 13 seer-3 ton adp "A" coil with txv. (Now I know better) I didn't go with their a/c install beacuse they were grossly overpriced. I did check with them and they said the house requires a 2.5 ton unit. Some of the experts here think the coil is oversized, and I agree. I am running a manual J to get my calcs and it looks like a 2 ton will suffice, but I am curious about one thing. Up here in Illinos, cooling is not the biggest need and I would like to know if I can use a properly sized 10 or 12 seer condenser versus paying the premium for 13. It's my thinking the short cooling season here does no justify the cost. Is it ok to do so with my setup or am will it cause problems later?