You can replace the bulbs yourself - they are changed from the back of the headlights, under the hood. The problem is the reflector and lens and 9004 bulb design.
Lots of people have followed this route before (brighter bulbs, over wattage bulbs, better wiring and relays) and still wind up installing the Euro lights, which are the lights that MB indended to be on the car.
Do a search in mercedesshop and you will find 5 or 6 useful links to lighting sites, dozens of threads on the conversion, maybe 50 or so individual opinions. Majority opinion seems to be Hella or Bosch Euro lights, Philips or Hella H4 (premium or vision plus) bulbs in standard wattage. This will give you great lighting. Optionally you can improve the new lights a bit more with a heavier wiring harness and relays.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E