Trading 670's, need advice if good deal

So the problem is, I have a Windforce 670 that barely fits in my case. It also dissipates heat in every direction it seems, I don't feel any heat exhaust out the back though (which is where I think it SHOULD be going). I think this makes it a bad candidate for an SLI setup.

My friend is offering me this 670 for mine: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
He said it runs a little warm, but his case is also small and poorly ventilated with no cable management.

So should I do the trade, buy another one of these, and throw them in SLI? Or just buy another case that's larger, and hopefully the 2x Windforce cards won't kill each other.