Grab the EVGA GTX460, it is known for it's performance increase when overclocked and the extent of it's overclocking potential(hope i phrased that well). The 465 has very high temperatures and increases the chance of a polar meltdown because of the heat it produces.
(Now the gtx465 owners are going to jump at my neck. )
EDIT: The card, that bad boy above, posted, has a better cooler. If you can spend a little more and take a chance with the mail in rebate you should buy that one, it will stay cooler under overclocking stress.