RS 220 received this morning. Thanks for the tip on SoundEarphones.com, Jeff. $1.99 for overnight delivery. Preliminary non-audiophile report: sounds damn good to me. My source setup is not dialed in yet, but I have played a variety of music file formats, resolutions and styles of music. 96/24 wav from iTracks (2L classical), 48/16 flac from HDtracks, 320kbps MP3 from MOG. I am indeed hearing remarkable things. Mind, I can't compare these to any wired high end headphones run with a proper DAC, but I'm hearing sound that seems to be centered in the center of my skull, with lots of stuff going on on either side, and lots(!) of detail that has never been apparent in tracks that I have spent a good deal of time listening to previously with my Sonus Faber Grand Piano Home loudspeakers and KRK Rockit 6 studio monitors, both of which I had thought were quite detailed. I don't want to misuse technical nomenclature like soundstage, separation, etc., but this is a whole new adventure in stereo listening for me. There seems to be a nice blend of treble, midrange and bass. For what it's worth, the RS 220s are in a whole different continuum than the Sony MDR-RF4000K wireless headphones I bought last year. I did notice a low level hiss when the sound was muted at one point, but it doesn't seem to be a constant. The headphones themselves seem to squeeze a bit too tightly, and the ear cups seem a tad firm (they definitely fight with my glasses,) but not a huge deal. So far I have connected the transmitter to a Pioneer receiver (VSX-1121-K) via analog and optical digital cables. I don't have a digital coax output right now. I may get an AirPort Express to try. I am using AirPlay from my MacBook Air to the Pioneer, and playing audio files from a USB flash drive plugged into the receiver. Everything sounds pretty great. I like female vocals, and listening to Heart, Suzanne Vega, and Diana Krall has been revelatory. The hires classical and jazz PCM and FLAC tracks I have tried sound extremely clear and detailed without being overly bright. These might not be the best choice for rock and pop, but they seem to be quite good. I think I am limited to 48kHz sampling rates by AirPlay and by my receiver, and maybe by the Sennheisers. I do wish there were a wired option like the Sennheiser PX 360 BT. However, for a fully wireless system I am super happy so far.