Howdy All
I thought I'd weigh in as I have M80's with the VP180. I was wondering about getting a sub with my setup as my concerns were the same - no boom! After long research I decided to get a sealed sub - think EP400. When it arrived I found the best location by following the always excellent advice from Axiom. After that I redid my audio setup and tweaked my speakers to small (set to 60 also per Axiom's advice).
Was it worth the effort? Yes it was and very noticeably satisfying. The VP180 and M80's opened up, no longer pushing all that bass. The sound was now more dynamic and balanced. Properly calibrated, subs aren't boomy - except when called for during movies
Not that my system wasn't capable before, it just opened up the bottom end below what the speakers could effectively deliver.
My space is smaller than yours so I was able to get a smaller sealed sub that works very nicely. If you decide to go sealed then I'd highly recommend the outstanding SVS SB13 Ultra or you could always get a couple smaller subs (EP400) as this will provide smooth bass while offering great dynamic range too.
