Even if it won't unlock that X800GTO will eat a 6600GT for lunch.
The HIS X800GTO with the R480 core and the factory installed ATI silencer will do 570/600(1200 effective) super stable. Pipes will not unlock on the HIS but the cooler is a plus. If he's not unlocking go for the HIS X800GTO. With only 12pipes and clocked at 570/1200 it got 5,800 points in 3dmark05.(at least with a Sempron 64 @1.9ghz) Lets see a 6600GT do that.
6600GT = 8 pipes, 3 shaders, 128bit memory interface, 500/1000
X800GTO=12pipes, 6 shaders, 256bit memory interface, 400/980(overclocks easily to 570/1200)
I was very impressed with the HIS brand card too. It is very quiet and runs very cool of course thanks to the installed cooler on it.
http://www.newegg.com/Product/Product.asp?Item=N82E16814161146