check out fatwallet.com, there were some guys there buying a tower with athlon 64 3400, socket 754, with 256 mb ram, and 80 gig HD's and DVD burners at compUSA during their midnight madness special, after $300 in rebates their towers were like $175 or something ridiculously low likethat, no BS. Then they would use the money they would get back on the rebate to buy a new PSU, extra ram, and an 8X AGP video card.
It can be done if you find a lucky deal.