Folks
The Levinson sub/driver/woofer has very specific characteristics. This
very high end integrated audio system is tuned to these characteristics as a system. This tuning is difficult, costly, and has yet to be surpassed in an automobile with the possible exception of the LS460.
Just plugging in a larger or simply a different woofer will at best sound as good and most likely degrade the response of the overall system. Which would be a terrible shame indeed.
Forget about the wattage of the driver. It does not matter in this case. The only spec that you are able to glean from the average driver spec sheet is the impedance (ohms). If you HAVE to replace the driver with a non-Levinson at least match the impedance. The characteristics of real importance are called the Theil-Small parameters (
http://www.thespeakerstore.com/gloss...ndingspecs.htm ).
My advice is if you don't feel like getting burned at a Lexus dealership, check out a used driver at a car parts lot from another LS.
I have been a "high end" audio nut for twenty years. Levinson makes some of the best audio gear ever created at any price point. They have been doing nothing but extreme high end audio components for decades. I think you can trust in them to deliver the best audio available at any specified (by Lexus) volume. I know I do.
Good luck and I hope I have been helpful.