An S 320 is O.K. if you do not crave instant pick-up power. If you do, then my suggestion would be an S 500.

Forget about the S 420, unless as said before, it is in excellent condition. The S 420 is basically a downgraded S 500 created for those who could not basically afford a new 500. At the used car market, the very small price difference between these two models is not even worth considering.

The S 500 in the States comes with nicer interior wood, although it also has the rear self-levelling suspension as standard, which could be a pain and expensive to repair.

__________________
A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]