Bigwater 745 is probably the best, you might also think about the Corsair Nautilus 500 if you want an external solution.
As far as the best goes, the Koolance Exos is the best water-cooler out there, and its external but retails for 300
Swiftech H20 Apex system is also one of the best , retails for around 250, but its mounted internally.
There are also some quiet solutions if your interested in that like the TT Rhythm. That runs around 200, cooling is mediocre, but very quiet
Or you can do a DIY, buy waterblocks and tubes and everything seperately, but if you're new to it, probably more trouble than its worth. Plus, you have to make sure the tubes fit and you have all the right parts, shrug...
Bigwater 745 should be enough for your needs, you might also want to look at www.Directron.com They're prices are usually cheaper than NewEgg, and I like them alot.