Here's what you want out of that:
1. Socket 478 is your friend. The chips are smaller and cooler. You'll still need a big fan, but the OEM CPU packs come with them. If not, a good one is available for $20
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2. 133Mhz bus. Yes, you want this. The 100Mhz bus is SLOW.
3. ATA drives are significantly faster than they used to be. For what you need, ATA is fine, and SCSI is still very expensive.
4. More cache is better with the P4, yes. The 133Mhz ones have 512K, which is enough. Celerons have less, and should be avoided. The new Celerons are socket 478 as well.
Mitch