Hi Mav,
You may simply prefer the slighlty "softer" sound (slightly rolled off treble) of analog connections over optical or coaxial digital connections. That is typically the most pronounced difference you'll hear going from an analog to a digital connection from any CD or DVD player(digital audio).
At the risk of raising the ire of JohnK, I'll have to side with Zimm on his suggestion that you think about upgrading the Sony AVR. As a former AV magazine editor in Toronto and New York, I've found that Sony AVRs somehow always have problems of one kind or another, including really weak amp sections that do not meet spec. That does not mean your Sony is defective; it may be quite alright.
However, there is no reason to believe the "sound" from your old Technics CD changer will be improved by switching to a newer player. In years of A/B testing of CD players at many different price levels, I have yet to detect a particle of difference in sound quality using musical programming as a source. Yes, there are measurable differences but at such residual levels they are inaudible with music. If an analog preamp output from a CD player is defective or poorly designed, or uses vaccuum tubes (!) it may introduce audible differences, although quite honestly I don't recall ever finding one that didn't measure well.
Just in passing, Nuance speakers were not terrible at all; they were designed by a competent US speaker engineer, Win Burhoe, who designed the original Energy 22 and some good speakers decades ago from Genesis. It's just that Nuance were sold with a lot of magic dust dreamed up by the late George Baker, a kind of PT Barnum figure in Canadian audio history, who for years was the marketing guru behind Energy, Mirage and Sound Dynamics. He later started Nuance.
Regards,
Alan
