The e7500 is newer, but if the 6600 is half the price, then I'd go with that. It all depends on the price. Also check your motherboard's "cpu support" section. If your board is oem by dell, hp, compaq, etc. then the e7500 may not work, unless it's listed under cpu upgrades on the website. In general, the e7500 will overclock easier, but it's not guaranteed.