-G Series for shitty integrated Intel GPU
-H Series for HTPC
-P Series for Performance systems (ie overclocking)
-X Series for Extreme (Pretty much a beeffy P series with extra feature/performance/price)
As I posted in your other thread, I'd highly recommend an X48 if you can find it, if not, a P45 based board from ASUS or Gigabyte would be my suggestion!
Edit: Make sure those boards support your CPU!
4x = S775 // 5x = S1156/S1366 // 6x = S1155