could you please tell me how upsampling works.
for example a cary 306/200 beside the hdcd
that you get you can upsample and can this
be done on regular redbook cd`s or only the
better recorded cd`s
I'll leave it to others to describe the technical details of upsampling, but, the unit you describe can be set in 44.1 mode with hdcd (if an hdcd disc) or in upsampling mode. You can upsample any cd, but if you upsample an hdcd disc, you will bypass the hdcd decode circuit (to my ears, it harshens the sound a wee bit). I have found upsampling to be fairly subtle, but can be more audible on some discs than others.
Upsampling does not increase the information but uses mathmatical algorithm to push digital noise out of audible band. The result is higher accuracy in DAC, and the cost is additional digital filters.

First of all, if you lose signal at transport section, there's no way to get the signal back by upsampling. Many people report the upsampling doesn't make much difference, I want to point out the difference upsampling can make is transport-dependent. In my experience a good transport is oh so important!

Second, upsampling introduces additional digital filters in the signal path, all digital filters have effect on the sound you hear. Many upsampling DACs now offer different sets of filters for use to choose, and different upsampling frequencies. They differ, and they are fun to play with.

I have a Esoteric DV-50 which upsamples CD to 24bit/1141kHz and upsamples DVD to 24bit/1532kHz, there are so many other options, I love it! Forget about 24/96!