Well i bought my friend a 6800le as a Xmas present, and XFX if memory serves, and it successfully unlocked fully to 16pipes and 6 vertex shaders. I know this is quite unusual for a le version but i got lucky, due to the reduced voltage on the le though the overclocking wasnt very impressive.
But unless you get very lucky too, i would have to recommend the 6600GT, due to the faster core and memory speed.
Either would be loads faster than your radeon.
Good luck. Enjoy.