Actually, you can use sata burners in the 2006 model Mac Pro. I have 2 samsung superwrite masters in mine (SH-S203N) and they work flawlessly.
SH-S203N is a bit old and harder to find now but it had light scribe and was rated as one of the last bulletproof samsungs before they cheapened their manufacturing process. SH-S203B was their great non-lightscribe version and SH-223B, SH-223N were their inferior quality successors but still nice drives. I haven't followed if the 243 versions are quality built again or not.
Pioneer is always a safe bet too (might be better for strictly DVD purposes).
If needing to burn to more than one drive at a time, I recommend SATA. For this, you would need to use the 'extra' SATA ports (that for the 2006 model were not intentionally disabled by Apple) and to wire them cleanly you have to remove the fan assembly. My fan assembly was so hard to remove without breaking it that I just took it to my local apple certified repair shop. I told them to use the extra sata ports and voila, it works like magic (after installing a patch from LaCie)
http://www.cdrlabs.com/ and
http://club.myce.com/f61/ are good starting points if wanting more info on drives.
As the poster above linked, OWC will usually steer you right and their customer service is great too. I'd call OWC because some features don't play nice without a patch or additional software like dual layer burning or lightscribe.