I'm almost certain you will end up spending about $200 maybe $300 doing the ignition, if your looking for more power your best off putting that money toward an ECU upgrade, pulley set, sprint booster, or and exhaust. I'm sure any one of these options will give you more seat of the pants feel in power... you'll probably make like 2-3 hp upgrading the wires and plugs, hardly worth it seems.

This is the problem with over engineered cars like MBZ, there really isn't anything left to upgrade, but if you do get the wire and plugs it would be nice to see a dyno on them, just to prove me wrong.