First try a stock cooler...Pretty damn nice and will hold a 2.4ghz pretty easy IMO...Mine did fine at 2.7ghz still....stock cooler with some aftermarket paste and this thing will surprise you....
I like the TT silent cooler ( or named something near this) as just a slight bit better then stock....For a bit more punch and more cash look at the SP94 if it fits your board or an xp90 (or 120 for bigger fan)