I can't speak to a class A, but we have a 34' TT with a single 15k AC and we do fine (and I like it cool!). Some of it might depend on where you plan to spend those summers and how cool you need things to be.
As for trade - we consistently see on here that trade offers are typically quite low. If you are looking at NADA or others, those numbers can be misleading for a trade. As mentioned above, you either need to own that a trade offer is going to be low and accept it (for the sake of convenience) or do the leg-work to make more by selling it yourself.