This is probably just me, but this is what I would have done:
Bought a Lite-On LTC-48161H Combo DVD/CD-Writer.
This writer also have very good write quality, and if you find a CD-R disc brand that the plextor don't like then try it in the Lite-On and the opposite way if the Lite-On do not like a media type.
With the plextor you get the nice quality measuring equipment named plextools.
With the Lite-On you may use all the nice programs that Mr. Karr Wang have made like KProbe for write quality measuring, and minfo for finding the media manufacturer as well as ltnflash to backup firmwares in Lite-On drives.
To me this seems to be the killer combination of writing quality, features and write quality measuring(both CD and DVD quality measuring).
Just my thoughts though....
btw, I have the plextor premium and it perform well if powerec is enabled(but writespeed drops to 24X at the end on many discs to keep the quality good) , with powerec disabled it's very likely to fail.....
waiting for the PX-708A myself as well.