One nice thing about having all MBs is that you don't have to keep track of as many different parts - they all come from the same place(s), and, assuming you stay within an engine range, you can swap parts/filters back and forth. Helps keep inventory costs down.

The early W124s are the simplest (and lightest) ones in the model line, and I would almost go so far as to call them austere in terms of features, especially by modern standards. On the flip side, while there are fewer things to go wrong, because of their age, the early models will probably have more things on the verge of wearing out. If you're planning to stick w/ MB, I'd probably recommend getting another 94-95 E320, since you have two of them already.

Of course, if you want to drive something different for a change, maybe you should get a BMW.