Suggestions for VGA cooler

I'm looking for an aftermarket solution for my Sapphire 4850. I've done some reading and have narrowed down my selection(s) to either the Zalman VF1000 or the Arctic Cooling Accelero S1 Rev.2; do any of you have experience with either/both of these coolers on a 4850? Mostly I just wanted to hear experiences regarding performance and compatibility (how well do they fit on the board, any modding needed, etc.). I'm not necessarily tied to either of these coolers, either, so if there's a strong showing for something else, I'm willing to give it a try. Thanks for any input!

IMO the AC Twin Turbo looks like the Scythe GPU cooler. It should perform around the same..the Scythe is one of the best GPU coolers.

http://www.newegg.com/Product/Prod [...] 6835185081