Misti, amplifiers simply don't work that way; they have no capability of performing a miracle by making speakers "come alive sooner" at lower volume level. Volume is volume.
I accept that the impact is driven by a placebo effect, but I do "find" more bass even at low levels (this time about 70db). They call it weight I think. The only non-placebo explanation I can offer is possibly power reserves allowing bass (without a sub) that a smaller power supply can't reach. Sames as the greater dynamic range I explained above. But that is far from scientific, and I'm too lazy to do true A/B testing for the group.
That is the most surprising aspect of the external amp issue for me. There literally was more music than I was getting - 2 to 3 db of sound peaks. I didn't expect that and i think it adds something to the experience, when you exceed my old amps comfort zone of 80 to 100 watts.