Well, I was going to post a reply disagreeing with almost everything you put in your original spec., but that seems to have already been done!!

Colonel Mitch and Phantom seem to have said what I would have said (ish). You want an i7 processor, 280 or X2 GFX card, reliable power supply (personally I like corsair and antec), decent ram (> 4GB these days would be good - probably GSkill, corsair or OCZ), not a ripoff keyboard (I still love my G15), bluray drive (if I was building now, I would buy one (if I had spare cash)), and there aren't many i7 mobos anyway right now, so either an Asus or Gigabyte for now I think. For an OS, I would still go with something 64 bit, so probably Vista 64 since XP 64 sucks balls. The case is always subjective, but you want something with enough space, and perhaps a removable mobo tray.