Wouldn't it be better to feed the speaker output to a separate Xover and then control the output to both the speakers and the sub. That way the speakers wouldn't get bass they can't handle well.
Subwoofer set up
How can I effectively use a subwoofer when my speakers go down into the range of the subwoofer. If the speakers are connected to the output jacks and the subwoofer to the subwoofer jack, both units will be reproducing the same frequencies at times. Even my bookshelves claim to produce lower freqs.