GoChurchGo,as a recent immigrant to USA from Australia, I had until very recently lived in a 1 bedroom apartment. It was hard to change that situation with no credit history in USA, and financial institutions not lending money to a legal permanent resident (not a citizen). Though not the same, I empathise.
If you haven't tried putting springs under the 4 corners of your subwoofer, I assure you of two things. That the vibrations will pass from your subwoofer into the foundations and frame of the apartment much less with springs, and the bass will tighten up and sound much cleaner, and will require less power to achieve the same audible results with springs. And futhermore, they will be one of the cheapest means up substantial upgrade to your system, while making it more neighbour friendly.
Someone here in this forum was selling springs relatively cheaply, I seem to recall they were even cryogenically treated as well?
https://www.youtube.com/watch?v=BOPXJDdwtk4https://www.youtube.com/watch?v=8Pd8UK6SZ_s