1. The latest version is 101E, which looks very similar to 101D, except the bass unit is shorter and squatter making the speaker looks fatter. Soundwise, it is said to be an improvement, but no chance to do an a/b yet.
2. Disagree 101D lacks dynamic contrasts. It can go from being eerily silent to earth-shattering bass, on top of its other attributes like deep and wide soundstage, realistic presentation etc (although in my view it does not produce the deep deep bass some are used to or expect from buying such expensive speakers).
3. yes its very power hungry, the more juice the better. i recall an old review of 101D in the absolute sound where they teamed it up with a not so powerful amp resulting in not so great result.
it sounds great with mbl amps and you can really turn it up and hear it go. dont have much chance to hear it paired up with other amps.
4. hope there would be many used 101D in the market but i dont see that many in the 1st place. i see an old 101C on audiogon still unsold. plus those puppies weigh a ton in their crates and its not easy to ship or deliver.