I have a dual-core 4800+ and at the moment they are not ideal 'games enthusiast' chips. That said I hear the next-gen games are going to take advantage of dual core, and even games like F.E.A.R and Quake 4 are taking advantage of this extra processing power at the moment.
I personally love it because I can burn video images whilst playing games, without a performance hit, which you would not be able to do with single core. The only game I had a minor problem with was Ground Control 2 which when ran made everything go really quick. I later learned that you can get games to run in single-core mode and it was as good as gold, so I have had no games that were incompatible.
The motherboard I have is the Asus A8N-SLI Deluxe, which is a good 'all-rounder', not particulary great at overclocking, but I was worried about getting an expesive doorstop if I overclocked wrong. Many review sites including this one rate it highly, but if you are a true games enthusiast, you cannot really look past the DFI LanParty range of motherboards, which you can overclock to your hearts content, especially with water-cooling.
Good luck with your purchase :)