Doom3 in 1600x1200 with 12x AA.
Not a good idea for a Radeon 9800XT. Drop it down to 2x AA or none at all, since Doom III is very forgiving about that kind of thing, since its so dark. Take the resolution down a notch too. And if its on ultra quality mode, bring it down to just high quality settings, because the difference is almost unrecognizable.
My 9800pro runs pretty hot too. I should find a heatspreader for the back of the core or something.