I can only comment on the D240mk2 and D400mk2 as I upgraded from the former to the latter a number of years ago as I use them to power a pair of Kinetic Audio Labyrinth t-lines which are fairly inefficient and like their current/power. I used the same ARC LS5mk2 preamp with both amps. They are remarkably similar sounding. Very liquid and non-metallic for SS designs. More to the Ayre side of the fence then the Krell side if that makes any sense. May be that they both D240/D400 use a very similar low-feedback circuit. Not sure but I couldn't have been happier with either amp. I feel like the D400mk2 is a more powerful and slightly more refined D240mk2. I kept my two D240mk2s instead of selling them when I upgreaded to the D400mk2s because I liked them that much.
