Kev, you seem to have a very fixed view on a general demise of soul CD sales and broadly it can be summed up on two key reasons -
1. The availability of free downloads, legal or otherwise.
2. Freebie promotional venue CDs.
Whilst I think that you have made some valid points, and I agree they will have affected sales is some way, but I really doubt that these reasons have impacted quality CD sales to the degree you imply.
The promoters of CDs that push out the same tired old tracks, time and time again with out any, or any worthwhile liner notes are bound to be impacted greater than say Kent, Grapevine or Soulscape. The effort that the quality guys put into their CD releases through research, artist and producer interviews, together with great mastering are I'm sure, major contributors towards their success, along with the confidence that the artists and publishing companies are getting their dues.
If things were really as bad and for the reasons you describe, I hardly think that Ace/Kent would have the size of catalogue they have today, and continue to work on additional CD projects at the rate they do.
If you want to identify the reason for failing CD sales, I think you should look closer to home.