@elizabeth
I have experimented with my system and can say there are amny things that contribute to lean sound. So the problem may partly be the speakers inherent nature, however there are plenty of things that an accentuate the problem.
I agree on #4, no power conditioners.
They cannot fix a difficiency in an amplifier's design. The resistance of the series chokes adds to the resistances in the primary circuit. They add yet another power cord and socket,more resistance. Here we are trying to lower the resistance in the primary and then go and add perhaps more than we have subtracted.
Do any power conditioners give their effective series resistance?