Hi   thx for your response.   Budget $200 (although I am in UK so am thinking about £150) and I had looked at the Aune T1 (currently available at £130) and thought it might be ideal...   So the K551 need a certain amount of power? OK but for reference the amp in the iMac seems to...

hello all   I have recently bought some AKG551 over ear headphones which I am loving. I find that I am mostly listening to Spotify via my iMac at best quality (320k OGG) and find these indistinguishable from the same songs played as local FLAC files played through the iMac headphone out.  ...