That's funny, lol. There's always an excuse to buy more subwoofers!
Bass frequencies are notoriously hard to contain. While there are a couple of things (as mentioned above) that can help you won't be able to prevent most of the spillover from your sub(s). I haven't read that article
@ASCTim linked above yet, but looks interesting. I've not heard having multi subs helping with lfc before. I'm gonna check it out after this post.
Speaking of which, some avrs do have some type of low frequency containment setting that can help a bunch. It's gonna rob you of your bass, but might be your only option for late at night listening. Talk to your neighbors too. Let them know you're concerned about bothering them. They'll appreciate it and might even be a little more forgiving as long as you don't abuse it with a lot of loud late night movies and music sessions.