I would look at IntelliChoice http://www.intellichoice.com/ic2/
which lets you enter a model car and determine operating expenses - both the 95 w124 wagon and the 95 940 Volvo wagon rate as excellent. I would also check http://www.nhtsa.dot.gov/cars/problems/tsb/servicemmy1.cfm
for the problems/technical service bulletins to see what kind of obvious problems the cars have. The 95 MB had 1 (instrument cluster), the 95 940 had 5 (3AC, electrical, seat track). Useful starting points IMHO. Good luck on the search.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E