Optima seems to be the favorite. I believe they now offer a model (Orange top?) that is correctly oriented for Mercedes so as not to need a longer battery cable.
http://www.optimabatteries.com/
No need for high CCAs to turn over a small 4-cyl. gas engine. Choose higher Amp-hours if you have a powerful stereo, etc. Hope that helps in making your decision! Cheers, Andrew Seidel.
Reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=20609&highlight=optima+battery