rather more than too little, from personal experience from setting someone else's rig up, nothing less than 700W, but would recommend another 100 - 150 W!
corsair have great and reliable PSU's:
what i did was put your specs into this:http://extreme.outervision.com/psucalculatorlite.jsp
and got a score of 648W
thats your minimum, so nothing less than 700W preferably 800W
(P.S. i used the GTX 465 rather than the GTX 460, the power differences aren't large!!)
Just my thought