I strongly, strongly, strongly (i could type that forever) recommend socket 939 AMD way before i would recommend a intel, especially for gaming. AMD's cost less and do more. I have to be fair and say there are some good intel chips out there but they cost quite a bit more for less
actual performance.
Example:
Intel Extreme Dual Core 955 (one of intel's best)
$1150
AMD X2 4800+ Dual-Core (one of amd's best)
$640
were not talking a difference between apples and oranges, its more like cherries and watermelon
As far as the motherboards, its pretty hard to go wrong with Asus. I really like there products, there reliable and affordable. Elitegroup works for some but i have burnt up 2 of them in my own machines so i dont buy them anymore. Maybe i push too hard, i dont know but my Asus board dont seem to mind.

I havent heard alot or used a ASRock board so i cant really comment on it.