[citation][nom]apache_lives[/nom]show me benchmarks with my usual apps running - voice chat, torrents, messenger apps, antivirus, and a slightly cluttered system - paint us a true image of that things are like, not some fresh rig with fresh perfect install.[/citation]
No game uses four cores fully, or even three. That doesn't mean that quad-core is useless for gamers, precisely because you can leave background processes running without them affecting performance. So the games would not be any more CPU-bound on a cluttered system. Loading times might increase because of fragmentation etc. and background file accesses, but that wouldn't show in benchmarks.