Personally, I think that is one the strengths of the D7/D9 in that they don't require beastly amplifiers to really boogie or sound-good. Since they are decently resolving ( some even say harsh, hot, etc... :) ) matching them properly is good advice but then that holds pretty generally with most speaker changes anyways. I replaced Magico S1s with D9s and kept the same preamp/amp combo (Sim 740p/Pass 250.8) with them for years mostly because I just really loved the sound. After realizing I could not get my 250.8 to leave class A bias at my listening levels with the D9s, I have swapped the 250.8 for a cheaper XA30.8 (30w class A) and that also sounds amazing with the D9s too in my opinion. I've also tried a Bryston 4B3 and Benchmark AHB2 with the D9s in my home and could have lived with either of them too..., but so far the Pass sound with the D9s are my favorite.
Cheers
Cheers