While I don't have the other cans, I'm on the koss side for the cost to fucking excellent sound ratio that the kph30i have. And you don't need an amp for them. $30 and you're done.

The kph40 is my next buy. Or the ktxpro. They use the ksc75 drivers, so I'm on the fence.

Anyways if I ever get something more powerful than my cx1993 then maybe I'll get the Hifiman's and hope the qc don't suck