Don't use a top-down cooler unless it's a small ITX or 1U rack build, they're much worse than tower coolers.

I second the Hyper 212 evo. If it's too big for your case, choose a smaller tower cooler.

The L5639 isn't a particularly hot CPU though, I used to crunch 24/7 on a L5638 with a stock intel 1366 cooler.