Okay, I feel that I need to chime in here.
1) Promise and Highpoint PCI ATA controllers can not handle ATAPI devices, only hard drives. The only PCI controller that can use ATAPI devices is the CMD 0649 controller, which is now sold by Silicon Image. This is not the same as Sil3112, which I have integrated on my motherboard and I have no problems with, personally.
2) Cheap PCI RAID controllers are the same on the controller level as their non-RAID counterparts. Not to say that this makes the RAID cards ATAPI-compatible, rather it means that ATA cards still won't recognize your CD-ROM drives
3) ATA33, as long as it's actual ATA33 (i.e. DMA Mode 2) is PLENTY fast enough for anything. All it means is that your actual transfer rate is capped at around 30 mb/sec. Since the drives "thrash," they are spending more time seeking (which is independent of transfer speed) than transfering large chunks of data (streaming is the only thing that benefits from STR, as outlined in the Raid0 article)
If I may, I'd like to refer to the "Cheetah on 10mb/sec Fast SCSI II" article that Storagereview published years ago, where they found that there was very little performance degradation in everyday use going from an 80mb/sec to 10mb/sec interface on a 10,000 RPM drive.
So, don't worry about SATA or PCI controllers, unless the motherboard controller is still bound by the 32gb hard drive size limit. If that's the case, I'd vote for the Promise Ultra100TX2 cards - I've gone through a dozen of Ultra100TX2's and Ultra133TX2's, installing them in people's machines, etc, and I haven't had a single issue with them, aside from the fact that the XP built-in drivers have the 127gb limitation. Update drivers and the drives 'magically' grow to their full size
4) Why use Socket370 processors anyway? $25 + cost of powerleap adapter is more than I've paid for used Athlon XP 1600-1800+'s ($25-$30). Cheap Socket462 boards as "commodity" parts now, as is PC2100 DDR, whereas P3-era stuff is so old as to achieve "specialty" part status. I imagine, if you wanted to put a little time into it, you could sell the P3-era gear and buy cheap Athlon XP gear without spending any extra money. With DDR being cheaper than SDRAM, you could outfit the machines with 512mb PC2100 DIMMs, for 1-1.5gb of RAM, making swap largely irrelevant.
Of course it's a slightly bigger project than converting existing parts into machines.