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.
Good luck on your decision