Bob,
It is true that you will not achieve truly integrated subs without an electronic crossover. That said, you still have to look at the practicalities of the situation. I would go with one sub (music is recorded in mono in the subwoofer's range, even when it is a stereo recording, with very exceptions). Use the crawl method to find the ideal sub placement. Ideally buy a sub with variable phase, low pass, high pass and slope choices. Or you can insist on ideal and do what I did, but it's a black hole as my signature shows.
