That PSU is weird, I have to say. What's up with that fan?
Your case is a full-tower
. That is the biggest form factor case and should easily be able to accommodate all power supplies out there since it's meant to be able to take on E-ATX motherboards and other giants.
I would say that PSU is something out of the ordinary and you should get a different one, since some of the reviewers have even said it's massive (and I doubt all of them have a case of your size). It is very odd, and it's not your case's problem imo, since the PSU mounting area shouldn't be too small at all for the majority of PSUs.
How much power are you looking at? Does it have to be 850w as you're running dual graphis cards? I'd recommend this Seasonic one if you want the best of the best at a good price tag: http://www.newegg.com/Product/Produc...82E16817151087