I have been a proponent of a tube somewhere in the circuit to give the 701s some character. Using an SS amp with a digital source is just too much sharpness for my tastes without EQ. Of course this is only my opinion and should be taken that way.
SS amps are cheaper per watt of power but when you are trying to get a little warmth out of the 701, the tube amps will do a better job. The tube amps cost more per watt because of the power supply needed. The 701s will not sound like a Denon or Senn because they are made for recording/mixing. Tubes will bring some warmth to that presentation at a cost. Budget tube amps will cut cost in the power supply. One option would be to use a tube output DAC or CDp into the SS amp. Another is a hybrid amp. This allows the efficiency of solid state with the warmth from a tube source. Yes it is distortion but all amps do. Tube amp distortion is more pleasant to the ear than SS amps.
Having to max out the volume to get the 701 to sing is undersized.