I would definitely not suggest getting the Athlon XP 3000+- I used it for about 2 months and was extremely dissatisfied with it.
I had 512MB pc2700 in terms of RAM.
At any rate, I decided to go with what I have now (pentium 4 2.8GHz and H/T-it works), and I am still satisfied with it after using it for about a month now.
I previously had a p4 1.6GHz, which lasted very well for two years. I upgraded mostly because I was limited 512MB SDRAM.
Upgrades are cool.
Intel P4 2.8GHz H/T
Windows XP Professional