I find the ideal volume depends on your whole system. But in general, the better my system has gotten, the less volume is needed.
Over the decades I have pursued this hobby, more power has increased the punch and fullness in solid state amps. Although, for less power tube amps bested them overall.
Looking over your system, if I were you I would look to upgrade my preamp before looking to increase the power of your amps. I would guess that a really good audiophile preamp would increase details and midrange bloom and have a huge improvement on the overall performance of your system. I would recommend the best used Audio Research, VAC, Conrad Johnson or Presto preamp you can afford. Then you can revisit the amp issue later.