APK,
I have the Promise SuperTrak SX6000 I2O controller card. It's a 6 channel caching card with 4 x 120 GB PATA drives. The problem isn't really with it's performance but with the storage capacity. I really would like to upgrade all these drives to 250GB versions using all 6 channels. This would be great however I'm looking into upgrading my server to dual-opteron's but the caveat now is wether there are drivers for the 64-bit version of Windows XP

I'm waiting for a reply from Promise on this one, as well as wether any of their cards will work or not.
I just got back a bid for this monster server however the pricing is a bit high. I expected that but I may look at alternatives as well if I receive bad news from Promise.
As for the performance difference between PATA and SATA drives, well I see a much faster load times between a RAID 0 array on PATA drives vs. SATA. Is it a lot, not a whole lot, a few seconds but it's very noticable with my gaming rig since moving over to SATA raid vs PATA raid.
It's got to be the sustained data I/O rates are just better with SATA drives in general, wether in single drive or a RAID array.