I moved from a NAP250 to HX75 to HX1.2. I agree re: mains - Dynavector amps seem much less susceptible to mains quality (although Naim may have addressed this with their DR amps?).
I think the positive effects of moving to Dynavector will be more pronounced if you decide to the bigger speakers in the Shahinian range- whilst the 250 made a very decent amp for Arcs it ran out of puff when I moved to Obelisks and began distorting when the wick was turned up. The HX75 had no such problems and the HX1.2 added more power, finesse and a lower noise floor - very happy with it