Double blind tests (countless of) find no discernable difference between flac and 320kbps mp3 or VBR. Miniscule even at 192kbps. Spotify premium uses 320. All grados use the same drivers so I'd be keen on high end model fakes and swapping sr60 drivers into them.
Hmmm that's interesting. I'm no audiophile but I feel like I can hear a discernible difference between a CD and mp3.