Thermaltake coolers normally look the part, but aren't very good when it comes down to what really matters. I would look at Xigmatek's or Prolimatech's offerings as they are some of the most bad-ass air cooling you can get :].
Also yeah.. I would down your clock a little.
Although you don't get right up to the dangerously high 73C mark, I would not want to be riding just below it. Knock it down to 3.0 until you have better cooling!
It'd be a shame to burn out your chip before reaching 3.9!