UT2004 will depend how demanding you are.
I thought the game was playable with a P3-866 and a Geforce3, but that was a long time ago.
It was definitely decent on an Epox AMD760 motherboard (EP-8K7A+? something like that) with a midrange Athlon and a Ti4200.
My standards weren't very high though. I'm not much of an FPS player and I don't compete online, I just play single player against bots.
I have an old spreadsheet from benchmarking the AMD760 machine and it says the CPU was a 1600/133, doesn't specify the core type, Ti4200 128MB card. I was getting between 30-60fps depending on map type/etc. I had the graphic details mostly set to "Normal".
Slowest map I tested was AS-Convoy. With memory clocked at DDR266 CL2, it ran 29.8fps at 1280x1024x32, 32.6fps at 800x600x32.
DM-Rankin was ~60fps at 800x600, didn't try higher res.
If you want maxed details or 60fps then it won't be fast enough for that, but it's decent.