Onboard for 3rd monitor?

doesn't the 480 support 3 monitors anyway?

Unfortunately the only single card i know of is the gtx 295, the 480 only has the 2 dvi and the 1 hdmi on the back, and requires the SLI to do so. :\

Alas i must depart for work, i put my faith in you toms hardware forums, i will return later tonight  

I think your motherboard may disable onboard graphics when there is a discrete card installed. But... maybe not.

Also, what OS are you using? Some early versions, like Vista and possibly XP could install only one graphics driver. Your motherboard and Nvidia will be two different ones. Windows 7 is OK with two different graphics drivers. I have tested that.

Take one of your monitors and install it in the onboard adapter and see if you can get it to work with the remaining monitor in the discrete card. If you are successful, adding a second monitor to your discrete card should be successful.

As an alternative, get a cheap second video card. Any Nvidia series 6xxx or higher card will work.

It won't work.
I was hoping for AMD to release an integrated 5200 with 3 screen support, but sadly they didn't and went with a 4250 instead.
It wouldn't actually help in your case, besides you being able to switch between the two.

Otherwise, you'd need either an adapter or a second 460, both in which are rather expensive.

yeah. And if you were to jerry rig drivers to allow for that sort of thing to happen, it'd definitely be very unstable.