How to make small room sound bigger

Dude, like half of my threads on Audiogon are about this. :D

I’d go to GIK, and use the room designer to ask them for help, but here are the gneeral principles:

• Use the best bass traps you can afford/fit floor to ceiling and floor to floor. This is either corner traps or soffit trap up the walls, and mondo traps on the floor between them.
• Use 244 absorbers in first reflection points.
• Use combination absorber diffusion between the speakers and behind the listening location. Don’t forget the ceiling at first reflection area.
• Directly to the sides of the speakers is a great place for diffusion. It can really help fill in the stereo image.
• The smaller the room the thicker the panels you’ll want to use to compensate for lack of locations to put them in.
• First reflection points matter, but only in combination with a full room treatment.  If all you do is place at these spots you will barely notice a difference.

All above plus you may want to try some of the Synergistic HFT. While my room  is larger, I've found using these behind listening position on side walls helps to further scale up size of room. This has been added to room treated mostly with diffusion, preferable to absorption for me.

What's with the list of speakers and amps ? Ones on hand or ones under consideration?  To make the room seem larger you don't want a lot of absorption. 

Combination of absorption and diffusion. Room acoustics vary from room to room. And some is personal preference. I would experiment with several different placement options. But yes, too much absorption will kill the room energy. 

Good luck and have fun! I've always found experimenting with room acoustics quite fun and interesting.