You'll deffinitely will be fine with that. My friend is running that exact PSU with an MSI 8800GT (Same thing as the 9800GT), with 3 HDDs, and a Phenom. He's been running it for six months without any problems.
312 watts ( 26 amps) combined max 12v should be enough, but on the low side for my liking. It's also very low for a current 460W. Antecs Earthwatts 380W has more 12v than that, and their 430W has 30 amps.
It's working for IndigoMoss's friend, which is a good sign, but as it ages, or hardware upgrades increase demand, it may not be enough. I'd buy a better PSU if you already don't own it. The Earthwatts are quality units and go on and off sale at Newegg, with rebates and free shipping they can be very cheap. (I paid $30 shipped for a 430W recently). You can get the earthwatts 500W for $69.99 at buy.com shipped free no rebates right now.
OT @ Invisik - tell me you upgraded that earthwatts 500W when you bought the two GTX 260's ?!? I'm guessing you just didn't upgrade your sig. I like those units, but that would blow me away if they could could power an OC'ed Q6600 and those cards.