Need advise, help, whatever with sub placement

[neos_peace]

OK, I finally got around to getting a diagram of my living room. The "X" is where my sub normally goes, and after experementing with a few other places this is where I get the best sound fom it. My question is where can I put another one and get good responce form it.

I tried against the wall to the right
I have tried between the couch's in front of that coby hole.

is there anohter place I might be able to get good responce.

I will be replacing my RW 12 with the HD 15, adn later I will be getting another HD 15

any idea's thanks in advance.



By the way I almost forgot, is it a good idea to put the HD sub on a riser or make it lift offf the floor more. Is rasing it off the floor at all going to help improve the soudn coming form it.