i would only say, to what troy posted below, that in my experience owning and comparing the 190, 390 and 590 units, that the 390 and 590 played music with a noticeably more refined, and laid back treble response, and with even more command/richness/tightness in the midbass and bass relative to the lesser 190 model (and rost, which i also still have)
this comparison and observation running through the balanced xlr analog inputs of the amps, with outboard dacs (sonnet morpheus and audio note dac 4.1 tube dac)
the 390 is the richest sounding of the three, the 590 had a touch more treble energy and the 190 the most
this perception may be due to how relatively forward/recessed the rest of the frequency range played in relation to the treble, but that was my impression
hegel says publically that they made adjustments/refinements to the preamp section of the higher 390/590 in relation to the lower units in the line (which by the way, are still absolutely excellent)