Yep... the GS AGP is a NV40 core.
So most should unlock.
U have a 6800u with higher memory clock.
Good bang for the buck unless u can find a good used 6800u for a killer price.
I just found a nice 6800U with 425 stock core and Zalman plus a killer price.
My ultra does 450 core 1200 memory no sweat so my performance should be close to a unlocked GS.