I would suggest you consider using an updated wiring harness (Metra 70-1786) that allows you to use the RCA ports on the back of the Kenwood unit. I'm getting ready to install a Pyle PLCD43MRB in my coupe & I'm using the upgraded wiring harness. Saves from having to make all the speaker wiring connections. My $0.02. Here are a few choices:

Metra 70-1786 Radio Wiring Harness for Mercedes 94-04

Metra 70-1786 Radio Wiring Harness for Mercedes 94-04

https://www.ebay.com/itm/264457826633?hash=item3d92ea3149:g:cAEAAOSwukRddNSN (I bought this one; Metra copy by Red Wolf)

https://www.crutchfield.com/p_120701786/Metra-70-1786-Receiver-Wiring-Harness.html?tp=2977 (Crutchfield Sourcing)