the 190-series is called the W201.
i believe the W123 evolved into the W124, as they are in the same class size. The W116 evolved into the W126.
the W201 was the first in the series that sported that modern aero look, with a bold pinched-up tail, and crisp solid looks (they say it got some styling cues from the C-111). The W124 was a larger-scale version of this.
aesthetically, the W201 and W124 lacked the chrome treatment and classic 3-box design of the W123, and in this regard, represented a departure from the "classic" benz look represented by the W123. (many also say the W123 and W126 were the last that had that famed solid closing door sound, though the W201 and W124 have pretty solid sounds too)
more interesting info on the Benz design history can be found at http://www.daimlerchrysler.de/classic/design/index_e.html