Senn HD650. They simply blow the HD280 out of the water, IMO (I have both).

If you mix through headphones, try these out. Quality and comfort and amazing results, without using monitors.
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Yamaha 920 / Yamaha DGX-670 / Maui 5 Go (2) / Senn e935 / Sony C80 / Tascam DP24sd / ATEM Mini Pro switcher (studio)