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Rroff, if you dont mind me asking. is your 260gtx sli cards running under the q6600 and the 750i chipset board. i was a big fan of 680i boards with sli but could never get a good oc on that board with a q6600.
My vote goes to the AMD Duron, I built a computer about 9 years ago for a friend using one of these cheap CPU's and it is still going strong.