UT2003, X²
UT2003
The UT2003 graph maps very closely to 3DMark 2001 SE's graph, which is no coincidence given their API roots and card usage. X800 XT is 2X as fast as 9800 XT with X800 PRO tucking in at the 73% mark yet again. DX8-class performance is a piece of cake to predict generally.
X²
We're nearly CPU limited initially, but 3DMark03's graph becomes prophetic when the cards are being made to work hard. X800 XT is roughly 2X as fast at 9800 XT again, with X800 PRO sitting at 81% of the XT's performance.