IMHO, all other things being equal, you will barely notice the difference between an IDE drive and a SATA drive. See, for example,
this article. However, SATA is obviously the way of the future.
My suggestions are:
1) check that you have DMA enabled for the IDE driver
2) look for a 10Krpm SATA II drive
3) raid a pair of 10Krpm SATA II drives
4) check eBay for some second-hand SCSI kit. I use here (and also look after 5 other computers with) a mobo with onboard U160 SCSI coupled to some 15Krpm drives. They really shift.
Before you install XP on any SATA drives make sure you have the drivers on a floppy!!!!