Ok - Here we go...
I have a Plumax Case with the Prolific ChipSet BridgeBoard. I am also using the BenQ firmware for the external because it provides a higher burst rate (47L9).
My Nero CD/DVD Speed Test for burst rate are as follows:
Firewire = 24 MB/s.
USB2 = 20 MB/s.
In order to support 16X you need a speed greater than 22,160KB/s (16X).
So the best you can do on USB2 with 20MB/s is 12X.
This is only part one in your quest to hit 16X. We only have the external drive set up that can hit 16X. But remember there are alot of other things that must fit in. Is you machine fast... Is you hard drive fast... Do you have builtin port on your motherboard... etc., etc.
Please go read the "Big External Case" thread - much more details are there...