I have cold feet now too on the ear muffys and the impedance, Basically i like My Xonar ST and want to put in muses and its got a high impedance amp inside, And as i said earlier my ultimate night time cinema (Oppo BD105) will be using whatever headphone i buy and it contains a high impedance amp inside for headphone out and from Headfi people say 300ohm seems to be the limit as well.
I just wanted a better headphone with more fine detail and a more airy soundstage than my HD595 which i think are too warm to my ears but people on Headfi say it will not be a proper match as X1 is a 30ohm phone which i never knew before. I look at some info on HD650's and people are saying WOW when they try them with the Oppo or STX because they go togeather beautifully. I have a set of HD650 reserved for £220 until Tuesday and the X1 is still £181 so i really have no idea what to do. I do not ever see me using a low impedance amp in future because the Xonar and most of the Oppo's and Recivers use high impedance amps for headphones