Questions - Subwoofers & Bass Traps

[BWLover]

So I got the sub in the mail and I love it. It's quite power for how small it is (10" in a 1 cubic foot box). I played around with positions and what not and ended up putting it dead centre between the two speakers. Anywhere else sounded uneven. One thing I did notice is that when the phase switch is on 180° is sounds much more powerful in my listening chair. As stated above I don't have bass traps. I have a basic understanding of room modes and how they effect low frequencies within my room. Am I correct in understanding that a particular low frequency will hit the back wall and bounce back and cancel out the next frequency coming out of the speakers? So if that is more or less correct, is that why the sub sounds more powerful at 180°? Because the sub is kind of doing the opposite of what the bass drivers on my speakers are doing, therefore making it more difficult for my room to cancel out the low frequencies? I am pretty sure this isn't the textbook way I should be doing things, in that my sub should be in phase with my speakers/set to 0°. I'm thinking that when I do get bass traps that I will be able to use the 0° setting and still have powerful bass, no? Also, if I were to treat two corners (instead of all 4) at once, should I do the corners behind the speakers or behind my chair? The bass is most powerful behind my chair vs behind the speakers. Also, I noticed that when music is on and I am upstairs above the listening room, that the floor vibrates the most above where the rear listening room wall is, vs behind the speakers, although behind the speakers is an exterior wall and I'm guessing more inert, is that normal? One other thing, the subwoofer cabinet vibrates quite a bit. The build quality of the cabinet could be better. I was thinking of putting 20-30 pounds of something on top of the sub. The sub is spiked, but I find its not heavy enough to really anchor itself to the floor. I did end up pushing down on the sub to get the spikes to dig into the floor a bit more (don't care about the floor in this room). But I've always understood that the cabinet should be as intert as possible as to let the drivers act like pistons. So would weighing it down help or just be a useless tweak?