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 Stagepas 100 BTRs / Senn e935 - LIVE
Roland RD 2000 / Tascam DP24sd / ATEM switcher - STUDIO