Adding the MKIII for this next round
It's no slouch compared to the other two, closer than i thought before comparing them A,B,C all together. It's definetly on the thinner side in the low mid, which reinforces me into thinking the MSE strikes the perfect balance in this area (RN6 is thicker). The soundstage on the MEST is obviously bigger, a good step wider than the RN6, which is only a bit larger than the MSE. Instruments sound great on the MEST, vocals are fine but not to the level of RN6, or MSE which are often to die for. The bass of the MEST is on the slower side, and the sub bass can get a little boomy too but there is less of it than both MSE and RN6. It's still a very enjoyable bass, more shy on chill genres, that can also hit hard on more electro or pop tracks. Only when compared to the other 2 monsters, it shows a little weakness there.
I should have added previously as well that RN6 highs are absolutely beautifully done, they are smooth, never tingling, you really have to push unreasonable levels for them to begin to get offensive even on tracks that are know for it, it's probably the best highs of the 3 ultimately. If you are into trebles, you ll love this set i think. It's so good that i forgot about them (which is the best sign). They actually remind me of the focal's beryllium highs and that's a big compliment in my book. All that with one EST, some accoustic voodoo going on there in the RN6.
I had to check a couple of times to make sure but yes the RN6 is even easier to drive than the MEST, it's not 2times less power you need (on a db dial) compared to the MSE but more like x2.5 or even 3x! Insane how efficient those are in relation to the big sound they produce (and how hungry the MSE is).