The obvious question is: What games do you wish to play? The 360 has decent quality graphics for its current games, but the games that are considered great on the 360 are generally not available for the PC. Likewise, the PC has great games that you won't see on the 360. If you want PC games that are unadulterated and/or unique to the format, then put $700 into upgrading your current machine (new cpu, graphics card, and possibly more RAM). If you want games unique to the 360, and don't mind less-than-stellar ports of some PC games, then put $400 into a 360.