More light from H4 bulbs
I tried 100/90W (or 100/80W) H4 bulbs and concluded that most of the advantages were almost outweighed by additional voltage drop in the wiring caused by the higher current. Apart from concerns of damage to the headlights, wiring or switches, I also had concerns as to possible damage to the bulb failure unit in the W124.
Recently I have fitted Hella "Plus 50" H4 bulbs in the standard 60/55W rating. They are supposed to offer 50% higher light output presumably by converting slightly more electrical energy into light rather than heat. The difference in light output is quite noticeable and superior to the 100/90W bulbs I tried. The "Plus 50s" also maintain the correct light pattern which the 100/90W did not. Hella also market a "Plus 30" which I believe also gives a noticeable improvement over the standard H4s (although presumably not as great as the "Plus 50"). Bosch, Philips and Osram all offer similar higher output versions in the standard wattages. In fact, I think the Hella bulbs are manufactured by either Osram or Philips anyway. Check any of their websites to see what's available.
I will be using any of these in future rather than risking damage with 100/90 or 100/80 bulbs.
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.