I would need to know other factors like what kind of a case it is and your fan configuration? If it's hot with one card it might be equally hot with the next if the setup isn't right.
I'm moving from an old Corsair 550D made for silent operation but only has 2 120mm fans in the front to my new Fractal Meshify S2 with 3 140mm fans in the front, much more airflow through the whole thing so I expect cooler temps throughout.
Just a thought, but I would address the case/fans etc first, and if you do have a good setup and it's still a thermal issue then look at other components. But without knowing your setup it's hard for anyone to say what's the issue here. Plus with new cards dropping soon, the prices on all cards is going to come down so it may be better to wait a little bit anyway.
EDIT: in answer to your question about if you can just swap the cards out and start playing, basically yes, but you will want to download the right drivers for it which is usually easy enough.