I have a W123. I upgraded to Euro lights. I have no problems with wiring with 100/80 bulbs. 80watts is plenty, but like it was said in the previous post, the reflectors make a big difference. Mine are in pretty good shape, and the glass is clean. Be careful when cleaning reflectors because you can wear away the aluminum vaporization coating.
I didnt put relays in my car because I havent had any problems with melting wires yet. lol.
PIAA bulbs say they put out higher wattage with lower current, but that doesnt make sense with physics. They wrap the coil less times, so it appears brighter, but I dont think it is. I have regular OSRAM blubs, and I like them.
Good luck on your lights. Try consulting this web page
See you later,