Damnit just wrote a whole post and had it vanish..i'll try to recap everything quickly.
-Noone said the 8150 won't run it ,just that for the same money you could get some extra FPS.
Also don't worry about changing brands, Catalyst is the software your ATI-cards use so it won't affect your CPU in any way and you won't have to relearn a thing.
-I'd even stick with the 8150 if you had the shop preorder all those parts. By asking this and having them buy them for you... you commited yourself by your word, even if you haven't paid yet.
Ignore this if you're buying out of stock.
-Might need a stronger PSU if you use crossfire and plan to overclock the CPU later on. 2 6970's will draw 500Wattt combined under load, and an highly OC'd 8150 will draw about the same.
Add some periphirals like USB , harddisks, DVD-drive etc and 750Watt will be insufficient.
Also if you have some extra cash to burn, strongly consider an SSD as the general windows experience will be night and day difference, aswel as CLOD loadingtimes without having to fiddle with RAM-drives and the likes.
There that's the gist of it, hope you still read this before heading off.
And please let us know your experiences once everything is up and running.