I've read about a few sub-woofers that have built-in internal amps such as the Wharfedale SW250 (250W), Wharfedale SW150 (150W) and Acoustic Energy Aego T 5.1 (200W). Most of the amps/receivers I've been looking at are 75 - 100W per channel. This is probably going to sound like a really stupid question but ........ if the sub-woofer has it's own built-in amp does that mean it's OK with a main amp that isn't anywhere near its own power output? Some centre speakers have a power output greater than 100 without having a built-in amp. Does that mean a 100W main amp wouldn't cut it?