A couple of things:
DON'T go for 64 bit Vista if you want to play games...The 32 bit version is far better supported.
See if you can push them on the graphics card (an 8800GTX or Ultra) Should be possible if you are spending that kind of cash. PSU SHOULD be ok, but I'd prefer a 600watt in there myself.
Should I upgrade to Windows 10? 8 reasons why you should upgrade to Windows 10... and 2 why you…