Actually, considering Mcconnel's requirement for a warm sounding combo, I would clearly advise against the H6, as they are anything but warm.
I also had the Sennheiser Momentum 2 over ear models, which are warm (and very portable), but the bass is quit bloated and mids and treble, while clear, are drowned out in the overwhelming mid-bass. They are also more colored than I like.
The H6 are much leaner, without being bright. I especially liked them for piano, they have a natural attack and timbre, but I stoped using them after getting the Nightowls.
The Nightowls sound like a good speaker setup in a living room, wide, deep, dynamic, invloving, complete and detailed without pushing details into your face.
Both the Sennheiser M2 and the H6 would be a step down from the Oppo PM3, the Meze 99 is highly acclaimed, the NightOwl is a steal at the current price IMHO.
An excellent review directyl comparing the last two is here:
https://theheadphonelist.com/honeyed-songs-in-the-forests-shade-a-review-of-the-audioquest-nightowl/
If portability is important, Neither the NightOwl not the Meze fare well....
Both have great transport boxes but are quite big. I take my NOs to work, but on an airplane it's really a hassle...
BTW, another HP that was reommended a lot was the ZMF blackwood, Ramnetin, who seems very experienced, recommends them a lot.