Why exactly are you buying such an expensive computer? I have a p2 400, and it plays Divx and mp3s fine. And with a decoder, I could play DVDs aswell. My moms p3 500 plays them just fine in Software. I don't like people who think they need the fastest computer just to do every day things.
I recently read in Maximum PC magazine, and somebody wrote in about a Power Supply on a p2 266mhz. They repeatedly wrote about how ancienct it was, and how they were afraid to take it apart because it was so old! Its only maybe like 3 years old.