Thanks for all the advice
They are using a P2 266 now, and even still are reluctant to upgrade because they think that what they have is fine. So my task was to find a complete system for VERY cheap so that they couldn't really say no to it, but I wanted to make sure that it would have enough power that it won't need to be upgraded too soon, and I just wasn't too sure about the Sempron. Again, thanks for your replies.