I have a 360 but il play it on pc because i want to play with my old gaming friends as well
Currently i've got a fairly average
AMD 64 3200+
2gb DDR400
X800 256 XL
However il be going for an upgrade this year and i cant be arsed to build one and have seen lower spec'd Alienwares dumping all over my higher spec machine performance wise so im going to bite the bullet and spend about £2000 (probably about $3200) on getting a high end Alienware, only I'll have to specify that it has 2gb as for some reason all their standard models are still 1gb only.
At some point I'll also get Windows Vista so that all the 64 bit and duel core stuff works properly and probably before i get that upgrade il get a 20" or 24" (depending on funds) LCD display. Having seen the difference a 24" LCD display makes on a friends PC its certainly a huge plus, but im not sure its worth it at current prices, the 20" widescreen displays certainly seem like the best "bang for buck".