Ben, the extensive double-blind tests that were published in my AES Journal about three years ago established quite clearly that at the consumer level the 44.1KHz sampling rate/16 bit depth of the CD standard provides all the sound quality distinguishable by human ears when properly employed.
In these tests DVD-As and SACDs of acknowledged excellent quality were "downgraded" to the CD standard by running them through a 44.1/16 ADC/DAC process. In the blind tests the "downgraded" output sounded just as excellent as the original material and couldn't be distinguished from it. The superior sound of the DVD-As and SACDs was due to superior recording, mixing and mastering, not sampling rates or bit depth.
