Due to its zero feedback technology the SM-70 PRO has won wide
acclaims as the most transparent, most tube-like solid state amp
and used as a mono block, the lowest cost True Balanced Amp in
the industry.

The new generation just introduced features higher power:

180 Watt on 4 Ohms above 10KHz in mono mode.
140 Watt on 4 Ohms below 10KHz in mono mode.
40 Watts x 2 on 4 Ohms in stereo mode

much lower noise (by the use of an epoxy-filled toroidal transformer)

and enhanced performance (circuit revision).