IMO, if I'd go MB W124, I'd get the CE model or the Coupe model. Rarer, exclusivity sometimes feels good. W124s are already old, have to dig ways to add charms to its appearance. Either you add bodykits or get a more exotic model/variant. I choose the latter, but that's just me. Or a 94 C-class is indeed more appealing.

Audi A4, same sentiments as Squala.

BMW, is my pick among the choice. It has its fair share of probs as the other Germans, high maintenance, not the best in space department, not the most feature-packed but i think it is the best compromise among the trio.
I just think the dash of the E36 is way too dated even compared with the W124 Benz or the A4.

Another suggestion if you indeed are eyeing on Germans and non-discriminating.
I suggest the 98 Volkswagen Passat GLX 4Motion. Price could be within or a bit higher than most of the choices but its NEWER for one and has Audi A4 underpinnings. Feature packed even with the Audi's Quattro 4 wheel Drive System, the 30valve V6 and luxury and convenience features not found on some base models on your choices.
You could opt for a lower model 1.8Turbo GLS variant if you want more savings.