Heheh, I would have assumed the same too... Until I saw this: Tom's Hardware Compare i7 - i5
I even managed to find your processor, i think...
That site opened my eyes a bit. Have a look around... You'll also note that the hexacore offering (the phenom 1090T) from AMD gets shat on by a large number of intel units
Here's a link to the Newegg.com - i5 2500k Sandy Bridge
. Newegg is an american site. They don't ship overseas as far as I know :'( .
As I said, the difference between the 480 and 460 is about 14 places... By forking out that little bit extra, you possibly extend the working life of the machine and potentially (if you ever crossfire or whatever nvidia are calling it for their gpu's), can get a serious bit of hardware. Just that little bit closer to your "beast" machine. However, its up to you whether you want to spend the extra coin.
Crossfire is using two video cards in parallel to increase your overall graphics power. Pretty cool. But it sucks juice (comparatively) and throws heat. Google it, there's some interesting stuff out there.
500gb will probably be sufficient, if it ever becomes a problem, you can add in another drive and not worry about it. Or alternatively, use external storage for stuff you don't actually need on your hard drive.