The PC1 doesn't take a load from the 501s, it buffers the load demand from the 501 on the mains and instead of a spiky demand request it presents a more even, sinewave-like load that keeps the mains clean. (Those spikes cause harmonics in the mains, that presents as noise in the system). Additionally, the PC1 converts the AC to DC and presents 380 Volts DC to the 501s, or whatever is downstream.
I'm using the Beethoven Baby Grands in an apartment now. They've got a small footprint and they're not too tall to fit in a smaller space. However, the Rowlands should handle every speaker that you listed with no problem.
Botti's trumpet tone is troubling because it's highly processed and doesn't really represent how trumpet sounds outside of processors. Still, I think of the "blair" as "scheen" or "sizzle", since "blair" is a negative term to us trumpeters, which results when the trumpet is not played correctly. On well recorded brass there should be a wealth of high overtones. Trombones should have a buzz or burr when played loud in orchestra music. That's a real part of their sound. Believe me, I've heard it in the back of my head more than a few times. ;-)