I intend to upgrade the headlights of my W203 C180. What are the best options available on the market and what are the names of companies selling these options.

 

Depends on what you're looking for. I would imagine something a standard Philips H7 LED upgrade would provide the best value in the modern era.

Then there are options if you want to modernize the look of your car. For example, the facelifted (MY2005-2007) halogens have the modern clear look, but can also fit the LED H7 bulbs. Or you can install the OEM bi-xenon HID headlights, which have the most modern look of the bunch, but these won't be LED.

Lastly, there are aftermarket options, but for those I'd be worried about headlight performance.

 

Ooooo they make those now?!!!
Will the lights flash like they do when you do Xenon upgrade without setting Xenon to present on the ECU?
( Due to lower power draw.)

 

Sadly they probably still won't draw enough juice. A resistor will still be needed. Also a large hole will need to be drilled into the cap to accommodate the heat sink. Just saying that it's possible in the modern era.