Ya... dual core chips for sure....make sure you get a high speed, dual channel board and memory. 1GB for each core at least .... probably more if you want your system to last .... DRAM prices are cheap now.
If you a serious gamer you may want to Look into SLI or Crossfire for your board.
I'm waiting till quad-cores become more mainstream to upgrade...DDR3 will be mainstream soon too.
But you can sit around waiting for the next wave of computer technology forever... so just budget and buy