I agree - there's not really too much point in upgrading your mobo yet, you won't see any real performance gains. If you really want to upgrade now, and don't mind forking out $350~, you could upgrade your video card to a Geforce 2 GTS Pro. But again, as SD pointed out...the new generation of cards is pretty close now 🙂
But definitely don't bother upgrading to a different motherboard - it's not worth it, unless your AV7 is giving you major problems.