Have a look at Zalman fans - which are supposedly the best for GPU cooling.
Heres some pics of a Zalman which was added to my graphics card on my old PC..
which previously kept overheating to the point that it would cause the PC would reboot until it was added.
Original RAdeon 9800XT. Had already been replaced under manufacturers warranty due to overheating, but still wasnt coping.
underside
Original heatsink removed
The Zalman kit
Fitting the Zalman
Fan installed
Completed
Graphics card back inside the case