1997+ Coupes definitely is your best bet. That is, if you can cough up couple extra grand for one. You will definitely be happier with revised tailights, bumpers, Parktronic, Xenon, and eletronic 5-speed auto tranny. But neverthless, C140(as well as C215) is still my favourite MB so far, with V12 R129s tie with E55 and E500 for second place..
If you can have that 1997 S500(assume it as full record, and no claims)for $60K +/- 2000, grab it!!!
Good luck, and keep us informed