well ... u have to know which amp u r insalling as 4 channel amp varies from 3K to onwards so atleast u should know which amp u r installing and what are the specs of it ..
and as u r going for one woofer setup so it better to get 308D2 as all amps are 4 ohms stable on bridge mode so D2 will give u better output ..
check > 2150ub has SUBWOOFER connection or not ?? if not get a HU with subwoofer option as this option works better than other..