I have only skim read what you have there mate, but try this;
In you BIOS disable the On-Board Sound Device and leave your sound card left in the PCI slot, connect all the relevant connections to the connection slots in the sound card on your PCI slot.
When you boot up your computer and go into the control panel, select "Sounds and Audio Devices", then select the "Audio" tab.
Make sure to set the "Sound playback" and "Sound recording" to the same device. Hit apply then you should be set to hear your sounds and music.
Also, what sound card are you using and what drivers are there?
If you still have trouble, I could setup a WinVNC (RealVNC) sever with you, a private one so I can try and sort it out on the fly, basically I could try to get your sound working while on my computer but working on yours. -- ONLY DO THIS IF YOU TRUST ME, I have never broke a promise in my life and I will never do so because I wouldn't live with myself... Though I will tell you now, I promise that nothing will be touched on your computer other than the primary goal for me to help sort out your sound, that will be it.
I would advise you to decline if you wasn't sure about the procedure and I am not making you do anything, all I want to do is help you out and hopefully get your sound working as it should
Good luck and hope you get it sorted out soon!
--Lee