For Blokdok, yes this is one a CLK ('99 coupe)

No problems with vibrations (as I said, a very solid mounting plate for the subs)
Though the Sony Xplod's do not come with a free air spec (they are rated for small sealed) and in most computer programs it will give you some crazy numbers if you input free air type parameters, the proof is in the end result.
I run 240 watts per driver (2 10") with the Sony XESZ50 reference system as source provider, and the XES M50 midbass drivers in the front doors (240 watts each)
This system is very demanding, and the subs do it justice.
If you would have told me that before I tried it, it would have laughed.
Not laughing now.
The reason I did it was to reduce install complexity, to be able to keep my trunk space and spare tire, and to have a "stealth install"
I am extremely fussy when it comes to cars and stereos (Sound Quality is very important) as well as a vehicle that is not all chopped up when you are done.
This type of subwoofer setup is perfect for those goals.
Also, I agree that the line level converter is a last resort, only to be used if there is no other choice at all. They really degrade the sound quality, and can introduce noise.

[This message has been edited by trent (edited 10-19-2000).]