Me. I had both the Monica 2 and Monica 3, and preferred the Monica 2. Synergy may account for this, as the Monica 3 seemed almost too powerful for my amp when compared to the Monica 2. The Monica 2, to me, sounded more organic and relaxed than anything else I've heard so far. It was a true joy to listen to, if way too finicky to use long-term.
And as John said, I don't necessarily think the Monica 3 was a step backwards. I just preferred the Monica 2.
Also, I have a friend who at some point claimed to prefer the HD600 to the HD650. I don't have an opinion on this as I've never had the opportunity to compare both with the same source. It also would probably not be appropriate for me to name the person. He's not a member here.