In the spirit of follow up, (and to celebrate a little), I finalized my choice for the ProAc D30R today. It's a great speaker and was, in the end, the easiest of the choices to make. I found electronics far more beguiling: separates versus integrated, tube versus solid state, used versus new; and the whole question of how--or even if--to integrate it all with existing home theater components.
Today I intended to audition an ARC SP20 (as a sort of stand-in for an LS17se the dealer didn't have yet but could obtain) with the ARC DS450 solid state amp. Demo system included a Rega transport and of course the ProAcs D30R on the other end. I found the ARC solid state amp very impressive, especially for well-recorded rock with a little dynamic range left. For jazz it was good, not always amazing. The bass was "grippy," as they say, and the mids were quite transparent and rich. Still I felt there was an element lacking from my previous session when the ARC VSi60 was pushing the show. Everybody says tubes with ProAc, maybe more than I've seen that advice for any speaker.
One thing led led to another and I found myself listening to an ARC 75se with the ProAcs, and it was a transformative experience. Talk about making those speakers sing. Before all this, I had no real listening experience with tubes. To go from no experience to one of the finest valve amps available with a tube-voiced speaker like the ProAc was disorienting and shocking. The staging and atmospherics, the tunefulness of the bass, along with the clear liquidity of voices and wood instruments, simply left me stunned. While the DS450 presented a vivid, detailed portrait of the music, the Ref75 *was* the music, present in the room in a visceral and tactile way, like some transparent and holographic labyrinth.
So I bought the components, the ARC 75se and the SP20, because what they do together is genuinely beautiful and there would have been no way to "unhear" it. I feel like I'm at the start of a very cool musical journey, and the ProAcs showed me the trail.