Verbatium is the only company that actually makes good quality DL discs - +R or -R.
I haven't tried any DVD-R DLs yet, but my Plex does very well with the 2.4x DVD+R DLs - and it burns them at 6x. The 8x ones don't do as well with the Plextor.
As for checking quality; the PX-716 comes with the PlexTools suite which can do it.
However, I prefer Nero's CDSpeed (available free at www.cdspeed2000.com
). However, it doesn't work with the Plex. Personally, I like BenQ's DW16xx drives for scanning. I use my DW1620 for just about every scan I make, although the 1625/1640/1650/1655 are just about as good...
BenQ 1655, BenQ 1620, LG 4167, Plex PX-716SA, Samsung SH-S162L, SH-S182M, Pioneer 111D, Lite-On SHM-165H6S and 1.9TB of HDDs to feed 'em and an X2/4800 to crunch for 'em.