I just recently upgraded my Sapphire 9800 Pro Ultimate which was cooled with the Zalman solution to a BFG 6800GT OC to which I have added an NV5.
With the 9800 Pro the Zalman got HOT until I added the optional Zalman fan, which was VERY quiet. The Zalman cooler looks super cool, no doubt, but it did not cool my 9800 any better than the folks have added the NV Silencers to their cards.
Also, the Zalman will NOT cool an 6800s memory -- even the stock coolers on 6800s cool the memort. I would wager using the Zalman would result in damage to a 6800, especially an Ultra.
Adding the NV5 to my 6800GT was a breeze, it is very quiet, moves heat outside of the case, and my GPU temps drop nearly 10c. It is an inexpensive solution and quite effective.
I suggest you forget about the asthetics and buy what works, man!
Cheers!
DJM