I am currently getting bids on Carrier, Trane and Rheem. The bids on the Trane and Rheem both came in very similar with 13 - 14 SEER and 4 and 5 tons. However, I just got a bid on a Carrier on a 19 SEER and only 3 ton and the installer cliams that will cool the house with no issues. I curenlty have a 3 ton airhandler and a 3.5 ton condensor unit outside. It is very old about 15 years old. It cools the house but it takes its time and it is eating me up on my cooling bill. My concern is that all other were suggesting going up in tonage but this intaller claims the house will be fine at a 3 ton but a high SEER. Any advice??