I have NEC3500, not 3520, but despite the different chipset, I've read they are pretty similar in features (in any case, I'm very far from being an expert). Pressed SL CSS DVD discs can be read upto 16x (just tested one recently for curiosity, with Nero CD speed & DVD decrypter), so there is a hope 3520 drive can do it, regarding the pressed disc is GOOD quality (generally they should be).
By coincidence... a week ago I purchased a [pressed, CSS] DVD I was to watch first time on my PC and surprisingly some pixelations appeared; so by curiosity I used decrypter and reading was complete but VERY, VERY slow. I tried with 3 readers (NEC & 2xLiteons). I was almost ready to return DVD disc to store but I decided to 'test it' on my standalone DVD player... and played flawlessly... Curious behaviours,
So, we can find out there from very bad to very good quality pressed DVD discs.
Suggestion: test another DVD disc and/or Nero DriveSpeed.exe so you are sure drive read at maximum speed.
EDIT: Simple Nero CD speed use help you to transparently configure drive to maximum speed. Download it and use it; maybe you watch a change in reading speed ... good luck