If you want precise integration between the subs and the main speakers, you need a way to measure the response. That means getting a measurement mic and measurement software. If you don't need that level or precision, just run some tones and listen for any cancellation that might be occurring. Use something like
this tone generator, and listen to frequencies around the crossover point for reduced output. If you sense a reduced amount of output around the crossover frequencies, there might be some phase cancellation occurring. in that case, switching to opposite phase
might fix the problem- but more likely, the problem will be a matter of room acoustics rather than phase mismatch, in which case no phase setting can correct that problem.
If I were you, I would just follow Hsu's placement and setup recommendation. That should get you to a reasonably good sound. After you get on that footing, there are more tweaks you can do, if you care to, but I think it would be getting way ahead of you and potentially confusing to dig into that stuff before you even have your first sub.
