Thanks again - the problem is solved.
As this might help others in the future, I looked at the Adobe link and then with a bit more research learned that my AMD HD6970 which is easily Open CL capable was not enabling it because if any residue of NVidia graphics driver still on system (my previous card), AMD's Open CL won't load up (used free software called GPU Caps Viewer (1.8.2) to get information about the video card).
So I had to do the following:
1. Removed those leftover driver components with "Driver Sweeper" - then tried to re-install the AMD SDK with Catalyst, but still got an error loading the AMD SDK. Why?
2. Learned that also needed to remove the OpenCL installer package (you can test this - if you get error message saying an instance of the installer already exists when you run openCL.msi found in a location similar to this --> C:\AMD\Support\12-8_vista_win7_win8_64_dd_ccc_whql\Packages\Apps\OpenCL64) then you will need to remove the existing "instance" of that installer
3. So removed that installer using a Windows Installer cleanup program (msicuu.exe)
4. Re-ran AMD Catalyst, rebooted PC, Open CL now shown to be enabled, and PS CS6 allows me to view images with full GPU settings.
Side note, I have fully cleaned previous Nvidia driver fragments in the past but over time they re-appear. Only thing I can think of is that my motherboard has Nvidia Chipsets (680i) and that there must be some sort of background updating going on that is re-installing partial graphics drivers. I hope this does not cause problem to keep re-appearing in the future, as that will be a PITA.