Troy as opposed to 4 Ep500s you would get far lower frequencies with the EP600 or EP800 as they are both tuned lower.
I'm just stepping up to my first 500, I'm in an old apartment with basically the same dimensions 15x19x7.5. though the back of my room is open to bedrooms and washroom, and one side is open to an equal sized kitchen. I find my small subs ineffective with my M80s, SVS PB1000 and a cheap 150 watt 12.
If you have a large opening on either side try facing your speakers away from it so you don't end up needing to pressurize another area of your house.
