Here we go: today's Fry's ad in The Dallas Morning News:
$230 for Q6600 + ECS GF7100PVT-M
$200 for 1TB Seagate SATA300/32MB, 7200RPM
$60 for 4GB PC6400 DDR2
$70 for Antec uATX Minuet 350 case
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$560
Throw in another $60 for 4 more GB of memory, and you've got what he's got, but with a bigger disk and much, much smaller case (it probably won't be as quiet) and for only $620 instead of $900.