Save money, and sell your 478 mobo and CPU and get a LGA775 mobo and CPU. The 775 mobo and CPU is generally cheaper than the 478 cpu's and mobos, and packs more performance.
If your thinking Intel, then get a LGA775 no hands down. If your thinking AMD, make sure you get a AMD64 socket 939. An AMD64 3200 winchester would work great. Even a 3200 Newcastle. I suggest AMD, since they cant be matched at gaming.