PS - You can always just pop an equalizer between the DAC & amp of course!!Can't see it's got tone controls. You could always use high level output type sub like my cheapo Mivoc G10 which has such. Feed the spkr wires from the amp into the sub per channel & then back out again from the sub outputs. Works great.
I suppose the filters on the E30/E50 work as tone controls to a certain extent. I always find old analogue amps Pioneer, JVC usually sound best on direct setting anyway. Certainly don't miss them on my Audiolab 6000a either!