I bought the Polk Audio DB840 8" replacement speaker that is named in youtube videos about replacing the Mark Levinson subwoofer. There is some discussion about replacing a Mark Levinson speaker with an aftermarket speaker. I went with the Polk($54.00) and it sounds fine. Does is sound as good? I couldn't say because before I replaced the ML blown subwoofer I didn't think to study up on the quality of the sound. I installed the Polk and it sounds fine, maybe great. That's very subjective. But it does sound like a high quality and working speaker system.
Interesting comment is that the price of the Mark Levinson is in the design and not the hardware. Old ML speaker weighs much less than the Polk but does not seem to have any distinguishing or different features.
Thus end that debate for me. Polk ($54.00 ) vs. ML(used -$300.00 - minimum)
R&R pretty simple. if by the time you read this , youtube videos still around, they can walk you thru it. One video has you removing rubber ring around new Polk speaker, one has you keeping it. I kept it and modified plastic bracket that goes BELOW speaker and allows speaker to seat properly on car deck.. This is the bracket that screws onto your rear deck . I secured this bracket with 3 little screws drilled into the plastic. Don't let these screws be too long as they will hit metal rear decking of car. Otherwise any little screw will suffice. The other bracket that is attached to ML assembly is no longer needed.
to restate: you throw away one of 2 ML brackets and use only the bracket which screws into car rear deck. drill new holes thur existing holes in Polk speaker and into plastic bracket to secure speaker to this bracket. I only used 3 screws. Like someone said this will only be critical if you roll the car.
I don't know the electronics theory but I followed instructions for 'shorting' voice mail coil. Why do that , I don't know? Does it have to be done, I don't know either? Its simple though. Get some wire crimpers and connectors and some short speaker wire and get after it.
It took me around 3 hours. if I knew what I was doing , under 2 easy .
Seat removal is simple. However when you start removing and reinstalling trim which is seated with those plastic punch pins, It gets a little frustrating. It is of course not automatic that you can line up pins with holes in car's sheet metal.