Hybrid Crossfire does/did exist, it doesn't apply to the OP though as it was only for the 3xxx series IIRC but it makes your 'fyi' slightly incorrect.
I was about to comment that you could xfire discrete with onboard graphics but I didn't know that was only for the 3xxx series. Thanks for that tidbit mousemonkey.
Safcfan1971, I completely agree with mousemonkey. You should wait until you upgrade your CPU; or at least wait until there's a game you're playing in which you feel your 460 is no longer adequate.