Anyone who's tried to put a subwoofer in the trunk of a W126 knows it won't work very well--if at all--because the trunks are so well sealed. You need to find a way to get the sound into the cabin. Then, there's the issue of where to put the sub without a big ugly box taking up trunk space. Here's the solution I came up with--working with the craftsmen at Roberts Audio in Louisville.
First--a custom panel that replaces the two clamshell storage units on the rear deck with 2-8" ports open to the trunk.
The ports are surrounded by real walnut burl--and the panel is wrapped in a tan leather or leather-look vinyl--not sure which--that matched my palomino interior almost perfectly. The panel mounts from the underside with just 8 screws.
Now--where to put the sub? Roberts created a custom, sealed fiberglass enclosure which fits perfectly in the passenger side trunk cubby. The enclosure was sized to accommodate 2-8" Kenwood Excelon KFC-XW800F shallow-mount subwoofers wired individually with audiophile grade 12 gauge cable complete with quick disconnects.
The carpet covering the enclosure is pretty close to Palomino--but not quite. Could easily be dyed to whatever color you prefer. These subs sound great with a lot of punch--yet don't require a lot of power. I ran them at 2 ohms with just 350 watts and was very pleased with the sound.
As for mounting the amps--Roberts made up a slick panel covered in the same material as the rear deck which mounts to the trunk bulkhead behind the gas tank. Plenty of room for 2 amps plus crossovers or a dsp. Unfortunately, the ink on the bottom plates of my amps transferred to the leather/vinyl covering--but that will all be hidden by whatever equipment you choose to mount.
And to connect it all to your headunit--I have 3-17' Stinger 6000 twisted-pair directional rca cables.
As you can see from the pics--everything is in excellent condition. As for fitment--these were in my 560SEC and fit perfectly. I assume the same would hold true for all W126 models--but can't say for certain. I'm asking $400 for the sub(the speakers alone are $300 at Crutchfield--$350 for the rear deck panel--$40 for the amp mounting panel and $40 for the 3 rca cables. (they retail for $25 each)
I'm located in Madison, Indiana--which is midway between Cincinnati and Louisville--if you'd like to inspect them in person. I'll also be happy to ship--though the buyer will be responsible for actual shipping costs.
If you need more info--e-mail is firstname.lastname@example.org
Thanks for looking!