One of the members at BW purchased Magnaflow cats, they had to be welded in but cost under $300 including installation. Here's a link to the thread, which has pictures. http://www.benzworld.org/forums/w210-e-class/1300647-alternative-cats-photos.html

Magnaflow has a great reputation, when I have to face this I think they'll get my business. Better them than the stealership.

Take care and enjoy the ride,
Greg