Michael, the people you heard this from apparently aren't very knowledgeable on the subject. First, there is no internal crossover in the sub; it's only a low pass filter which rolls off the sub above the selected frequency. It has no effect on the speakers, even if they're wired through the sub (that's just a straight through connection carrying the power from the receiver without any processing inside the sub). The L/R speakers are still powered by the receiver; the internal sub amplifier can't power anything except the driver in the sub.
The bass management of the 6003 does a precise job of dividing the frequencies between the sub and speakers when the speakers are set "Small" with an appropriate crossover, typically 80Hz.
