M4-ATX and had trouble. I sue and Opus 360W and it's great. As far as gauged to the PSU I would run 4-8 GA to a dist. block. You will see the gauge of the PSU wires to be hooked up is rather small, 16-18G I believe.
Sound is a whole other department. Personally I sue and OLD soundblaster live 5.1 card ($10-20) on ebay and the KX Custom Audio Drivers. I delivers some incredible sound. Some use onboard sound, some use large PCI Digital cards, I would search.