Should i get 8 or 16 gigs of ddr3 ram?

as long as the memory you purchase is compatible with your motherboard, and you PSU is 400 W or better for your graphics, go for it, your money. A waste dual booting when Windows 7 has a compatibility mode? Brand is not an issue you probably get "Geil" brand cheaper, they all work the same and yes Geil has a heatsink. 16GB is an awful lot of ram?