The Metrum and Concero are on the switch, and I can say that one of them does NOT sound like all of the others when level-matched. But I aint' saying which!
Okay, I'll give you a Christmas present. The Metrum Octave does not sound like anything else I've had in this test so far. Not night and day different, but different enough that it was readily apparent within seconds.
Enough for now, I've literally only listened to 1.5 songs, but figured I'd put the worriers' minds at ease.