Otto,
You are totally accurate in your assumptions. My integrated amp is a Jolida 1501 RC, which doesn't even have a subwoofer output -- everything goes to the "high" input on my Hsu VTF-2 sub. The sub has variable crossover, from 30-90 Hz.
And yes, I'm trying to integrate the lil' buggers. I never thought of going outdoors to do a test, but it makes a lot of sense. I'll see what I can do. Pity my sound system and my PC are both on the 2nd floor, sigh . . .
Anyway, thanks for your help. I now have a much better idea on how to attack this particular issue.