I must admit that I was very skeptical that the Pioneer would look good in a Benz dash. However, I think it looks right at home in my old W123.
I have a Kenwood head unit in the W124 and it definitely doesn't look nor sound as good as the Pioneer in the W123.
However, the W124 has a pair of 10" subs..
so it is louder.
I would go for either Nakamichi, Pioneer, or Blaupunkt. However, some Blaupunkts are kinda ugly.. choose wisely.
OR!
you could try E-bay and with some luck you'll find a decent radio out of a wrecked or upgraded car!
Good luck,