Believe it or not, there's a compound out that outperforms AS5, and it's called Tuniq TX-3. It's less a grease and more a gummy substance, and thus more difficult to apply (you'll need something like a credit card or your driver's license to spread it about, and it takes a steady hand, about an hour, etc etc), but once you get it on, it's awesome. It's non-conductive, so if you "colour outside the lines" so to speak, it won't hurt, but it's still a good idea to clean up. It's specifically designed for Direct Touch type sinks, like the Sunbeam Core or the Prolimatech Megahalems (I use the Xigmatek THOR'S HAMMER [Yes, the package has it in all caps]), and has an easier time filling in the gaps and stuff. Another good sink is the Ultra Chilltec.
[EDIT]
Apparently, Tuniq just released TX-4, which has all the benefits of TX-3, but cools all of a whole degree cooler than the it's predecessor.