It doesn't really give more power, it just reduces resistance. A single run of 1/0 is adequate for pretty much every daily system. Once you start getting into setups have have high current demands, that's when need to look into multiple runs.
more runs of 0awg reduce voltage drop and increase the power your amp is capable of receiving. Probably wont notice giant gains(maybe) but at least 2 runs wouldn't hurt for that system.