Coming previously from a B&W 805N paired with Yamaha amp, so far my listening with my Kudos C2 with Nuprime is that while female vocals play loud volume wise, singers like Adele and Whitney Houston sound like they ran out of lungs (lack big openness ex: during the song 'I will always love you'). When I play large orchestral music like Beethoven 5th or Dovrak New World Sym., sometimes they sound ok while other times I can't seem to get the speakers to play with enough speed, tempo and musicality. I'm guessing these symptoms are attribute by not enough 'juice' from the amp.That does not sound like a power thing. If there was a lack of power, you would be describing distortion but this paragraph does not seem to do that.
So it is possible that 'tweaks' like a power cord and fuses might help. They both help in the same way: both devices can have a voltage drop across them which can result in a measurable loss of power. In addition (in particular with the power cord) if there is a loss of high frequency bandwidth in the AC power delivery, the power supply can't always charge up fully. This is because the rectifiers in the supply often only conduct for a very short time at the peaks of the 60Hz AC power waveform. Those short bursts of conduction are high frequency; if the power cord limits that the supply or supplies might not charge correctly. One consequence is that IMD can rise, which is quite audible.
IOW there really is physics behind why these things work.
You might also try different interconnect cables, shorter speaker cables, a different preamp or source! Its very hard to walk into a situation like this and simply point at one thing and definitively say that its actually the problem!!