i've got a 2 channel amp of the older series of US audio amps, with a 12" US audio sub, and its very reliable, has good features, and is very punchy. this is when US audio was made in the US, and you know, because they're predominantly purple.
the autobarn us audio series (which is blue and silver) is made in china, and unfortunately, is of a lower build quality. i hope your 15" is of the older series