Re: Upgrading speaker wire
Keep in mind that he wants wires for a Gigawork G500 5.1 THX. I don't think that it's very adequate to use high quality cables for a pc-set.
To give a rough hint on wire diameters:
<10m --> 1,5mm˛
<20m --> 2,5mm˛
>20m --> 4mm˛
Also, don't get crazy about the wires. Make sure you don spin them around a power cable or similar conductors. How long will the cables be?
Audiatur et altera pars!