Much better off...the 7900GS will totally ANNIHILATE the 8500GT. The lower 8 series are only good becuase they offer DX10 however the 8500GT will never play any DX10 games with playable frame rates.
Well all DX10 cards came out too early since there is no DX10 for at least another 3+ months. However the 8500, and 8600 came out too expensive for their performance.