Grimace is right about a few things here.
Silver is the best conductor of electricity but corrodes extremely easily. Gold is used because of the resistance to corrossion. Expensive wire has one advantage. It generally has more strands and is therefore, more flexible. The conductivity would be the same. I see no reason for not using the chassis as the ground in an electrical system. It is common, actually standard, practice to do so, and will not result in any degradation of performance if implemented properly.
A bridged amp will not result in any audible difference in SQ, so quit the misinformation.
