Thinking of adding a second sub

[racrawford65]

Currently, have one E15HP. Mostly music with occasional movie.
Listening room is 16x12x11 (11 is average height of ceiling as is tiered).
Opens to left side to den (~22x20x10) and behind to foyer (12x6x11)/dining room (16x12x11).

As per title, thinking of going duals. Even out bass response and a bit more output.

Least expensive option is to add a second E15HP. I may need to place sideways, with driver pointing to side wall about 3' away (which I don't think is an issue). Alternately, would need to slightly rearrange furniture/carpet so driver faces room, which isn't a major issue.

However, due to footprint/placement options, also considering either dual L22's or dual F8's (Dave has posted elsewhere how great these subs are with Towers). If I changed models, I'd either try to sell my E15 or use it (probably only for movies) by moving it behind/aside seats where I can easily turn amp on/off manually.

Thoughts?