get the accelero Rev2 from Arctic cooling. It has also a "turbo"module, basically 2 fans that attach to the heatsink.
Very easy to mount, results are impressive with extremely low noise.
I have one on my 512 8800GT ... in full load after hours of gaming the GPU core is at 52-54degrees. In idle is at 43..45.
I cannot emphasize how good, silent and easy to mount this heatsink is.