I've got a WBK38 on a 900tbird at 1066, with case fans my temps are under 45C most of the time.
But, running at 1333, I'm gonna agree that you'll want more than a WBK38.
If you ever plan to watercool it may be a good temporary investment, but, if you gonna keep it aircooled then you'd save money in the long run to buy a Glaciator or Swiftech MC462. Sure they're over $40, but if you spend 25 now, and then decide you need more a few months later, then you'll be spending well over 65 total....
For 25 bucks I'd go for the WBK38, but if your talknig about putting that on your setup, then I too would reccommend something better.
Mike