My heads huge. I don't have much to go by other than $50 Sennheisers from 20 years ago and my Siberia v2. I had to stretch my Siberias until they cracked and even still, I get headaches from wearing these. I believe its due to my ears not fitting completely inside.
Anyways, I was first interested in the ATH m50x, and then branched out. The HD598s and HD600s are on my radar.
I need them to be stretchable to fit my huge dome and ears. Comfort is king. Sound quality and build second :D
For reference, I can only can handle 1 notch on ballcaps.