More important is which Mac, how much RAM is on board, what apps do you intend and what OS version do you own? Good coordination among all those things will make your Mac experience a happier one because not all combinations work well.
You do not state what OS version, but if you are not already on 10.7, with a 2008 box I would stay with 10.6.8 until I was really really sure 10.7.x was not going to cause issues.
-Allen Wicks