I'd personally skip on the Soyo and get the Abit NF7-S Revision 2.0. motherboard. I personally believe it's the best on the market, and it's actually cheaper than the one you listed on
www.newegg.com . It supports a higher FSB and higher RAM speeds/quantities. It also has SoundStorm onboard sound, which is better than most soundcards on today's market. The only motherboard that gives it a run for its money is the Asus A7N8X Deluxe, but it's a bit more expensive. I'd go with the NF7-S.
The processor you chose is excellent for non-overclockers. An Athlon XP 2800+ runs at 2.08 GHz, but the 2800+ model name means it's the equivalent of a 2.8 GHz Pentium 4, and you see how much they cost.
If there is one place to spend a good bit of money on, it's RAM and the videocard. If you know how much you want to spend on the PC then I can tell ya which videocard I recommend.
-Lasereth