Help with the listening room please...

Thanks for reading my thread.

I am in the process of trying to make my listening room sound better. My listening room is on the first floor of a townhouse. The room is 13 X 16 with a 10 X 10 bump out along the 13-foot wall for a total of 23 feet long (somewhat of an "L" shape). My goal is for this room to sound as good as I can get it to sound for 2-channel music. The floor is concrete, & the walls are insulated with a firewall behind the framing. I think the insulation is pretty good on the walls. I use five echo busters; 2 behind the main speakers, one in the center, and two for the first reflections (even though first reflections aren't a big issue because the room is open on both sides of the first reflection point on the side walls).

My speakers are on the 23-foot wall (on the side of the 10 X 10 bump out); in essence one of the speakers has about 12 feet before it's next to the sidewall.

Here is what I'm considering:
1. Insulation in the ceiling - The ceiling has about 12 inches of space that needs insulation blown between the joices. I'm certain the ceiling insulation would help out. Does anyone have a "preferred" insulation for inside the ceiling? Has anybody insulated his or her ceiling with stunning results? I’m wondering if the sound (bass, mid-bass or high frequencies) won’t travel throughout the house as a result of insulating the ceiling?

2. I'm considering building a wall about 5ft long perpendicular to the 23 foot long wall to somewhat separate the listening room from the 10 X 10 bump out. If I build the wall, both my speakers will be about 2 feet from a sidewall.

For building the wall, I'm thinking of using either 2 x 4's with double drywall boards & insulation or 2 X 6's and heavily insulating the wall without the double drywall boards.

I guess I'm looking for some suggestions if the sound in the room would benefit from the additional wall. While bass is not a big issue, I want a better, more accurate sounding room. I feel like I'm losing bass along the long wall because one of the speakers has about 12 feet before it reaches the wall. I guess I'm thinking of the wall as a bass trap. Would this help the room?