I just recently built my new rig for gaming purposes. I did a lot of searching for the right kind of setup. I came to the conclusion that the Intel e6400 was the best bang for the buck since it can be OC'd quite well. I would recommend getting the Zalman 9500 for a cooler.
As for the motherboard for the 775 socket. I decided on choosing the eVGA 680i motherboard. The 680i chipset is the best for running dual video cards. I currently only run one right now, but it still runs great.
Comparible wise, the Asus P5W motherboard would be a better choice for running a RAID setup, but would perform slower on the dual video card setup.
The eVGA 680i motherboard also has had some issues running high speed memory. I don't know how accurate that is, since I'm running 2GB of Ballistix DDR2-8000 and haven't had any issues at all. I ran through a 4hr memory stress test and no errors or lockups at all.
I've also heard some people going with the Asus Striker which is on the 680i chipset, but has all the bells & whistles to go with it. Price ranges on these boards are around $250-400.
I am actually kind of in the same situation. I am building a new rig C2D and looking for a good mobo as well, I am not going to be overclocking so that isnt an issue I would like to see what suggestions you get.
well now that you know what cpu your are going to use, you still need to find what video card going going to get. next is the memory, and remember to check the mobo's compatible witht he ram. if your not going to oc then you have many more options. but you might as well spring for the oc capability, because if you are using it for gameing its always nice to have. also you need a price range. try newegg to look for the specs you want then try hitting up price grabber to shop around. newegg usually has pretty good details on the hardware and the reviews are too bad.