The Nforce2 would be your best bet right now IMO. If you are looking to overclock, look into either the Epox 8RDA+ or the Asus A7N8X Deluxe. The Epox 8RDA+ will generally o/c better than the Asus, but the Asus is no slouch either. It basically boils down to what features you want and how important o/c'ing is to you. The Asus has a more robust feature set with nice extras like S-ATA, dual LAN, and included digital output (Coax SPDI/F), but the Epox is a good deal cheaper with slightly less "frills" if you don't need the extras.
Both boards would be excellent choices to build upon considering the components you have, but if overclocking is most important, the Epox is the one to get IMO.
I hope this helps..