That's a good question. With the 20" rears you may have to lose the spacers or have them milled down to keep the fenders from crunching on the bumps.
The good news is that you can "fine tune" the ride height with various size spring pads available from Mercedes-Benz dealers.
I'm a big fan of the Eibach Pro Kit and would definitely install them. Unless you want to go 4 wheeling...