Just wait until you get some hours on them. I don't want to debate whether burn-in is real or imaginary, but I definitely noticed a difference in my K550's after I put a few miles on them. It might be the pads forming to my head, or maybe it really is break in of the drivers, but it definitely wasn't my brain getting "used to" the sound.
I also put the headband on my arm and squeezed it so that the band is more round and fits my head better. Out of the box the headband was П shaped and now it is more ∩ shaped.
If they sound this good now, can't wait until there's some hours on them, for me that'll take but a few days, as for the headbands shape, can't say I've any issues with it, but maybe that's because I have a relatively flat head...lol