i currently use a p4-2.5ghz celeron d with a biostar p4vma-m socket 478 board. most of my customers are not into gaming or only low level gaming so they usually get the cheap systems as can always upgrade later if they need to.
i don't do gaming or very little as i use this as a tool to fix other computers. right now i'm working at putting back together a bki810 400 celeron, 256meg sdram, 52x cd burner & 40gig hd with xp pro for my computer & model workshop on the third floor of our house.