i'd recommend socket 754. From all that i have heard, every new 939 board has some issues, most of them having to do with dual channel ram.
but if you want 939, go asus over gigabyte. God gigabyte sucks hard. no tech support, can't download updates cuz their webpage is in taiwanese or something, more problems than any other 939 board.
i know from experience. been working on my gigabyte system for 2 months, no success. still get random bsod and crashes.