A few years ago most people had passive subwoofers, and were using a spare amp to drive a passive subwoofer. Dolby Digital started to appear- and people upgraded to active subs due to their adjustability. However nowadays with better crossovers in the processor (settings of 40,80 & 120hz) you do not need another crossover further down the line (in the sub amp module) So it's more preferable to go for a passive subwoofer with a external amp (otherwise paying for a crossover in a subwoofer which isn't used) Also you can change amps easily, and adjust volume from the racking. Thinking about a SVS CS-Ultra, as I don't need a crossover, and prefer to get a powerful standalone amp rather being lumped with the built-in amps. Comments?