I strongly advice NOT to use your writer for READING cd's. The Plex40-reader you have is one of the best there is, so only use your writer for reading if there is no other choice. You'll destroy your writer when using it as a reader. The laserhead is much heavier and reading asks to much of the mechanism, so your writer will die faster.
I don't know which writer is the best for SD2-copies. Maybe wait a little more longer; it COULD be that Plextor releases some SD2-compatible firmware after all, and then you'll have a great combo with the Plex40 and some plex-writer.