Ok.... I got everything wired up and soldered. I had tested. Started playing music and it seemed fine. Then the real test - I ran 'Field of Dreams' - something I had prerecorded on my WMC - Wow it sounded really cool with 'The Voice' coming in all the different directions. But - A problem was immediately noticeable:
The center channel sounded a bit like an AM station. The actors speaking sounded a bit like they are muffled, or maybe even over modulated. I checked some other recordings, and later live TV. The problem was still there, depending on what I was playing it would be less or more apparent. Like the connection is not good. I messed around with what connections and settings I could last night and this morning, and now I'm at work, and nothing healed the issue. I'm not sure yet, if it is my wireing job, or if it is my Realtek audio driver, or WMC.
For RealTek settings I tried bumping the Default Audio to the highest (192000 something).... and I left the 'speaker fill' setting checked. - I did mess around with the room configuration screen.
In WMC I did set up the Audio configuration settings, and change it to theater mode.
Steps to proceed to see if it is a hardware wireing job issue: 1) I can switch the two 3.5mm wires in the back of the computer - and then move the 4rca's in the living room appropriately. Then see if the issue now moves to a different channel. Which means I need to figure out how to open up the wireing jobs and diagnose (d'oh!!!)
By the way: The monoprice 'ground loop isolator' did not work at all for me. When I plugged it into the connection, it just turned my wires into radio receiver, and I was hearing a local radio station loudly. - When I talked to the tech guy at monoprice (he said it would go from F to M as expected one-way), it came with no markings on which direction to connect it though, and wonder if it was designed properly at all! Or if it was actually designed to work M to F.