I've got a DS2 with a i7 3570k and x2 7970 GE's. I also mine BTC. Only when it is pushed to the limit do the GPU's get noisy i.e. mining BTC / GPU computing. Gaming is not enough to do so. GPU's also have independently different temperatures, the second being 13C cooler than the first under load.
I've also got an FD R2 waiting to be built. If there are questions once I've built it, I'll answer them.