To attempt to respond to the questions asked about Amarra. I am using the full version of the software, not Amarra HiFi. I can't speak to how good or bad HiFi is.
I have converted a number of files from Flac to Aiff using Amarra. They can be converted at their native resolution (e.g. 24/88) and can then be managed through ITunes and the Apple Remote app, and played through a USB 2.0 connection, using the Amarra plug-in, to a network streamer capable of accepting the USB connection (like the Cambridge Audio Stream Magic 6). The file is transmitted and received at the native resolution, according to the front display on the Cambridge unit, and not down sampled.
I believe it is true that in order for the file to play through iTunes without Amarra, it must be down-converted to 16/44. But I am not certain.
I have converted a number of files from Flac to Aiff using Amarra. They can be converted at their native resolution (e.g. 24/88) and can then be managed through ITunes and the Apple Remote app, and played through a USB 2.0 connection, using the Amarra plug-in, to a network streamer capable of accepting the USB connection (like the Cambridge Audio Stream Magic 6). The file is transmitted and received at the native resolution, according to the front display on the Cambridge unit, and not down sampled.
I believe it is true that in order for the file to play through iTunes without Amarra, it must be down-converted to 16/44. But I am not certain.