Anyone interested in reading a little more about the process of upsampling, oversampling, interpolation, dither, etc. and how it can benefit(or hurt) the musical signal may find this interesting from the Perpetual Technology folks(see link below--sorry if someone else already referred to this). I found the Level III explanation(see link at the bottom of that page) to be the most interesting and it doesn't take all that much time/effort to read. What I took away was that it seems like it is the companies that go to the trouble of creating proprietary interpolation algorithms to meaningfully increase word length(i.e. not simply just adding dither) in addition to the upsampling that are the ones that are really taking CDs to a higher level with this concept(obviously a lot of non-upsampling players sound fantastic too). In addition to the PT P1A, the Audio Aero Capitole(STARS system) and I assume the dCS Purcell do this to great effect--anyone know what Electrocompaniet does with the EMC1(24/192)? This makes sense to me, but it also again makes the important point that all upsamplers are not created equal--not by a longshot.
http://www.av123.com/pt_interpolate1.html
Tim