I have more luck with LiteOn than other drives for ripping...although I will say that I haven't ripped all that much with my latest one.
As for the Full Paranoia mode in CDex....go to Options -> Settings, and click on the CD Drive tab.
In that screen, you'll see an option called Ripping Method, with a drop-down menu box. Click that, and choose Paranoia, Full.
Be aware that this may take longer than a "normal" rip.
