Lion King - thanks for the suggestions.
I don't understand what you mean when you say that the reampling process is lossy. Are you refereing to the way these particular plugins work or the process in general?
I know that the question of upsampling is open to debate. After all you are not adding any more information to the CD datastrem, just interpolating between the samples to increase the frequency and adding filtered noise to increase the bit depth. With the dCs Purcell, you can change the frequency and bit depth of the upsampling using the romote control while listening to the music and I can assure you that the sound just opens out and becomes more natural when you go from standard 16/44.1 to 24/196.
The technical explaination from dCs seems to be related to the brickwall filter in the D/A. With the higher frequency, this is nowhere near as steep and is far higher in frequency anyway.
I would have been happy with my existing system, except for the fact that it was all stolen last week while I was away on holiday and so I have to find a replacement. I will replace the Elgar DAC, but before spending $6000 on a new dCs Purcel, I would like to see if the same effect can be acheived with a $99 sound card and some software!