Which dvd-rom to copy 4X onthe fly?

I want to buy a new dvd rom player for copying dvd+/-r’s on the fly at 4 speed.\Which one should I buy.
I prefer the Plextor 116 or te pioneer 120s, or is ther another one that is better?
I have the Plextor 708 and is wotking fine, but which dvd-rom player should I use next to the Plextor 708.