Hi Foo,
I'd agree with JohnK on the RG-59 as being entirely adequate and your not needing RG-6.
Your idea of using a laptop with the isolated power supply may be a solution, but frankly I'm not experienced with HDMI/grounding issues using a home theater PC in a system.
Of course we all want dead-silent noise-free systems, but from a practical point of view, without a lot of tedious trouble-shooting, it's almost impossible to entirely eliminate all noise from a system.
I think the goal of achieveing no audible hum/hiss from your listening area when the volume is advanced to a level that would normallly generate very loud sound with CD or movie playback is a worthy one and achievable without becoming obsessively preoccupied with eliminating all audible hiss/hum with your ear next to the speakers and volume control fully advanced.
Regards,
Alan
