I have been using the 50 watt Mystere integrated (KT88's) with the D2's for several days now and the sound is beautiful but I think the D2's really benefit from an amp that can take control of the woofers. I liked the Mystere on previous speakers because it created a very full and spacious sound on less than full range speakers. With the D2's being full range speakers they are already very full and spacious on their own so I feel like the 50 KT88 watts are really not letting the bass response of these speakers live up to their potential. Everything else is great though. I loved the Mystere with my previous Tyler Linbrook Monitors and I suspect tubes would do great with either the D3's or D4's.
My suggestion for D2's (and D1's as well but I have not heard them) would be either a more powerful tube amp than what I am using, something that can really grab hold of the woofers, or solid state. I have also been using ice amps and I absolutely love that combination with the D2's. With class D the woofers are in iron fisted control. It's really astonishing what deep, quality bass will do in regards to a 3-dimension, enveloping sound. Keep in mind it's not just about bass response either, even in the midrange and high end I prefer the ice amps over tubes with the D2's because of the clear, resolving, un-etched sound. With previous speakers I preferred tubes over class D. With D2's I prefer class D. I don't have a class A or AB amp on hand to experiment with and I'm sure there are plenty of great combinations in that arena as well. Keep in mind too these comments are based on 4 days of listening with fully broken in D2's. Hope this helps.
My suggestion for D2's (and D1's as well but I have not heard them) would be either a more powerful tube amp than what I am using, something that can really grab hold of the woofers, or solid state. I have also been using ice amps and I absolutely love that combination with the D2's. With class D the woofers are in iron fisted control. It's really astonishing what deep, quality bass will do in regards to a 3-dimension, enveloping sound. Keep in mind it's not just about bass response either, even in the midrange and high end I prefer the ice amps over tubes with the D2's because of the clear, resolving, un-etched sound. With previous speakers I preferred tubes over class D. With D2's I prefer class D. I don't have a class A or AB amp on hand to experiment with and I'm sure there are plenty of great combinations in that arena as well. Keep in mind too these comments are based on 4 days of listening with fully broken in D2's. Hope this helps.