That is kind of what I came to as well, after originally posting here with the question, and listening to other amps/preamps in my system. I had some stuff (amp/preamp combos) that retailed for $15,000 (not the highest end, but pretty darn good) and the system improved, sure. More detail in the background, strings and piano sounded more realistic, bass a little tighter. It was nice. But, at 2x the retail price of my old stuff, it should be. And, we aren't talking a huge difference: if I didn't have the cash to double my investment in amplification (I don't) then I won't be sorry about listening to what I have. I could spend a couple thousand and get the amplification marginally better, but if the speakers aren't able to do much more with the signal, what is it worth?
At this point, I am leaning toward a speaker upgrade. With regards to why I am looking at the D1's without hearing them: I would have a money-back option if they didn't work. I love my Linbrooks as well, so anything that has a similar sound (musical, detailed, quite realistic) but is improving on it would be a + in my book. These are just easy to listen to, no matter the amplification, and (not being trained in music, but just enjoying it at a consumer) they sounds pretty close to the "you are there" experience, at least as much as can be expected by trying to duplicate a full orchestra in a 400 square foot living room!