Here is 8800GS 384MB and 768MB benchmarks
Expreview.com - Extra Hardware News Report! » Blog Archive » [review] Palit GeForce 8800GS 384MB & 768MB
8800GS 384MB at stock speeds is faster than HD3850 256MB
8800GS 384MB and 768MB gets higher FPS than 8800GT 256MB if you play games at high settings
8800GS 768MB performs better than HD3850 512MB
8800GS 384MB does outperform HD3850 512MB, if you omit the low FPS scores
Expreview.com - Extra Hardware News Report! » Blog Archive » [review] Palit GeForce 8800GS 384MB & 768MB
8800GS 384MB at stock speeds is faster than HD3850 256MB
8800GS 384MB and 768MB gets higher FPS than 8800GT 256MB if you play games at high settings
8800GS 768MB performs better than HD3850 512MB
8800GS 384MB does outperform HD3850 512MB, if you omit the low FPS scores