You have a nice setup, but I'd make a few changes if I were you:
Get the Abit NF7-S 2.0 motherboard. It's simply the best overclocking Athlon XP motherboard on the market. NewEgg has it for $99. Definitely get the Barton 2500+; you can get it to 3000+ speeds with a CPU fan.
Don't waste the money on the soundcard. The Abit NF7-S 2.0 has onboard SoundStorm sound which will perform as well as any soundcard on the market. It also has 5.1 Dolby Digital outputs for fiber-optic cable.
The videocard will do very well. Someone said it didn't perform much better than the TI4200...that's just not correct. The midrange newer NVIDIA and ATI cards don't perform much better than the TI4200, but the newer high-end cards do. The FX 5600, Radeon 9600, etc. are the ones that don't do much better than the TI4200. Even a regular GeForce FX 5900 will do a hell of a lot better than a TI4200. At $200, it's a steal. If you really know what you're doing with overclocking the videocard, then get it. If you're not sure about it, I'd go ahead and get the Ultra.
It doesn't matter what wattage the PSU is as long as it's over 300w. The thing to watch for is quality over quantity. If you want a good PSU, buy a Sparkle or Enermax. Do not buy a POWMAX or RAIDMAX and expect quality -- it's not gonna happen. My brother has a 400w Enermax. It's 100% silent with TWO fans on it. He's running FIVE hard drives, CD-ROM, tons of fans, lights, etc. A 400w POWMAX wouldn't even turn his computer on.
The RAM looks great. Another choice would be Corsair if you're gonna go into overclocking (I assume so with that CPU
).
The GeForce FX 5800 Ultra is the dustbuster model. It's pretty powerful (around 9700 Pro status), but way too damned loud.
Good luck!
-Lasereth