Dual Core or Core2Duo? The Core2Duo's pretty much destroy any previous Intel chips, even at almost half the clock speed eg. 1.86GHz E6300 will trounce a 3.2GHz P4 950 Presler.
An ASRock ConroeXFire eSATA-II with an E6600 in it will outperform most, if not all, AMD rigs - even overclocked ones, although the differential is not so clear-cut in games where the graphics cards often play a more important part than the processor.