I know a lot of those games are CPU intensive. I would recommend spending a bit more if you can on the CPU. Also, the core 2 duo is a much better processor if you can afford the upgrade. Even if you get a lower end c2d, it could help.
You should be fine on RAM with 2 GB to start, especially with XP. Also, that is a lot of hard drive space. You could cut one of those out to save money and buy a better cpu/video card. Also, I don't think you will need a sound card for a budget pc. Most users only get those when buying a really good computer. For a budget pc, the onboard sound should be fine.