Vmoda would be good. I have the ATH ESW9 which I like to recommend. I find them smooth and versatile. Some may disagree on versatile. M50 not very portable. There's always good ol Senn HD25 variations. Beyer DT1350 as well.
Burn in seems to just "bring it all together" for me. Doesn't change the sound per se. Just blends all the parts of the stew. Headphones can sound a bit stiff out of the box. These are flexible membrane drivers after all. Need a little running in.