What is my next step to a better sound ?

Useless to discuss changing anything until you say what you think the current deficiencies in the sound are and what you are wanting to hear that you do not currently.

Have the people indicating the DAC is the problem actually heard it? I have not, so can't say, but Arcam in tandem with DCS has done some good things with their DACs over the years.

If the SOny transport is operating properly, I would not expect much if any difference changing that, but anything is possible in regards to jitter with any specific device and how it conencts to the DAC.

If you have any other CD ready devices with digital out, it might be worth trying them and compare.

Or, ripping to computer and playing back via a Logitech Squeezebox Touch or similar device is a high quality, quite reliable solution I have found.

The thing that bothers me about the Rdac is the name. It seems to be designed to capitalize on Arcam's use of the highly acclaimed DCS ring dac technology in one or two of their legacy devices, but that is not what is used in the rDac. Their web site references the relationship with DCS and the use of other DCS technology in the rdac, but not the ring dac itself which I believe is DCS's crowning achievement.

I do not think it is good business strategy for DCS to license their bread and butter technologies to companies offering products at a fraction of the cost. That's probably why the Ring DAC is not available in any Arcam gear anymore.