I have a 2800 sq ft house with 2 2.5 ton AC units and 2 furnaces. Everything is 14 years old.

One of the 2.5 ton units is out of freon, and I think its best to replace it rather than pay $400 to get freon and a leak fix and maybe it doesnt hold.

The contractor's Ive talked to agree that if I dont replace the furnance as well, the best I'll get is 13 seer even if I get a 16 seer unit. I cant see replacing the furnance when it might last another 6 years or more.

Does it make sense to buy a 16 seer unit anyway, on the theory that I'll inevitably have to replace the furnance before too too long?

The contractors are telling me different things on this.

Thanks.