Car appreciation... the aesthetics, the engineering, etc

You already have, with your Daimler-Benz W124.
Love W123s in all forms, though like most cyclists I perv over the S123 (Estate) the most. They're worth quite a lot here in CA, although practically every Diesel is being fed WVO or BioDiesel now. I'd prefer a petrol one myself.
An S124 with the 5.0 V8 in it would probably be my ideal tourer right now though.

I used to have a W201 190E, I miss it terribly.

There was a original AMG 123 5.0L? wagon turn up on one of the US Merc forums. I expect you've seen that. Nice.

WVO doesn't do for any longevity, IME, even in IDI Merc engines. Seen someone kill a twin tanked W201 2.5.
All my cars for the past 5 years have run on finest B100, brewed "right here" in East London.