aA,

The K70x need a good break in of several (3-4) hundred hours. Initial sessions will be light bodied presentation, some sibilance, no bass impact. They will do best with a hybrid or ss amp. They are very detailed with an artificial high and about the largest headstage out there. When broken in, the highs will smooth out and bass will gain accuracy and extend to about 30~. The headstage extends outside your skull. They do well with natural instruments and vocals. Not real engaging with high energy genre and bass heavy music.

I'd suggest a hybrid amp with a digital source and an ss amp with analog. A full tube amp would be expensive because of the power supply needed to run the well. I'd suggest an output of at least 500 mw. The K70x are 64ohm but not very sensitive. AKG says 200mw max power rating but experience is complex material needs more reserve current. The K70x will scale well with better front ends and are ruthless on poor recordings.

A couple of things to help the break in. Wash your pads a couple of times (notice the position of the donuts before removing them as the thicker part goes to the back). This will get the foam to conform to your skull quicker. This will help the bass. Positioning is important to get the best bass too. They respond well with pink noise at moderate volume.

And after doing all that, you may not like them. Re-sell on these are around $190. If you do like them, responses have been favorable on a re-cable. They get another level of clarity and speed. I don't think I'd re-cable unless perhaps a silver coated copper with an analog source.

Negatives include plastic sounding mid-highs that throws off the natural timbre and pitch of stringed instruments. They have no bass impact and present everything in an airy presentation. Little weight in the mid-lows down. Many people have problems with the headband bumps on their heads. A little leather conditioner and a hard fold at the crown of the headband will loosen them up quicker than just wearing them.

And the worst thing is you can never wear them in public. They look to some like toilet seats.