anywhere I can find opinions on these older plextor drives?

This site has a lage list of different drives and their DAE speed, but the oldest Plextor I could find was the PX-12TS which has a DAE of 8x.

As for what to do with a stack of SCSI drives.....I am sure it is possible to run multiple instances of CD paranoia (linux) and extract from several of them at the same time - so you just sit there feeding in a CD every X/Y/Z minutes (where X is the average lenths of a CD in minutes, Y is the number of drives in use and Z is the extract speed 4).
Of course one gooe IDE drive would do fairly well against 8 of thoes SCSI drives.