Any reason you excluded the RE262? On the higher end of things they are probably the first earphone I think of when 'warm and relaxing' comes up. On the budget end of things, I can make things harder for you by adding the Xears TD-III. Not the greatest build quality but then they are cheaper than everything else you're considering except maybe the PL50s. No review of them in this thread yet but I did write something up here.
And of course from your list I'd pick the MDs assuming you don't find copious bass antithetical to your relaxation needs.
I am looking into RE262 and what I think I will do will be getting both RE262 and BM3 and seeing if I like any of them. Later I will try to pick up a pair of used MDs, they are incredibly expensive in the EU and much cheaper in FS forum.