The machine gets slightly sluggish when there is any major IDE action (like when an antivirus scan is running) but goes to hell in a basket when DVD burning.
I'm thinking a Vantec SATA card with a LITE-ON SATA 16X DVD on one channel and a WD 80 gig SATA on the other (where the target files are stored) will fix the problem.
Upgrading the motherboard isn't really an option, this is a low power "on all day" box used for browsing, Photoshop, webpages, very light retro gaming, storage (hence the RAID mirror for safe data) etc. and it does them very well.
I'm just looking to spiff up the DVD burning end of things and have the machine a bit more usable. The 4x speed of the DVD burner doesn't bother me but the machine getting dragged down while burning does.