You can use one sub. You can run it on a single channel of a two channel amp, or you can bridge the two channels. Note that bridging a two channel amp essentially makes it a one channel amp (able to output a single unique signal).[url="http://www.the12volt.com/glossary/glossary.asp?l=B" said:from the12volt[/url]] "Combining two outputs of an amplifier to use as one, usually to a woofer. The provides an increase in power output (wattage) necessary to reproduce lower frequencies at higher volume levels"