If you're looking into closed-circuit water cooler, Intel has it's own solution which I can tell you from experience is identical to the Antec Kuhler H2O 620. That in turn is similar in performance to the Corsair H70 I believe, the H80 being slightly better and the H100 being the ultimate in pre-built, closed-circuit water cooling solutions but only fits in a handful of cases.
In a heatsink-air solution I read that the very best still are the Noctua D-14 and Phanteks PH-TC14PE. Both are massive though, and quite expensive. Again, will not fit in most cases that are 20cm in width or less.
I myself am looking for a smaller-factor, more moderately priced solution but if you're looking for the best in CPUs, my thoughts would be, better not skimp on the best cooling or a good case like the HAF X or similar (which ironically I love to build almost as much as I hate its' looks!!!)
http://www.coolermaster.com/product.php?product_id=6653