The P5B will own the 680i at overclocking any day. It's also rock solid. P965 chipset. I have that exact mobo, it's great, get it.
I also have that case, hard drive, and DVD burner, excellent choices there.
That's an awesome PSU, but overkill for you. This is a great PSU that will suit your needs:
If you're going to do any even slightly serious gaming, you'll want a better video card, even an 8600GTS would be better. This is assuming you want DX10.
Creative sound card drivers suck, no other way to put it. I wouldn't get a Creative. This isn't a bad card in that price range:
You'll probably want some DDR2-800. This is only $25 more, and with the money you save getting the Silverstone PSU, it would be worth it. This is an awesome deal:
I dual boot XP and Vista with very similar specs to that, it will work just great. Install XP first.