I'm no expert by any means and I've never experienced one of those car subs, except by registering on the annoyance factor. But my room and layout is almost exactly the same as yours. 17 x 11.5 x 8-12 vaulted in an L shape opening into dining and kitched and I'm perfectly satisfied with a lowly EP350.

https://docs.google.com/spreadsheet/ccc?...amp;usp=sharing