I've got my LS6's in a mid size room (18'x19'), and my acoustic treatment project I did a few years ago really made them shine. I put DIY tri-traps in 3 corners, 48"x24"x4" panels behind each speaker, and three 48"x24"x4" panels on the back walls. Interestingly, I tried treatment panels on the front wall (between mains, behind center channel) and it deadened the mid's and high's a little too much, same for the first reflection points, so I took them down. The tri-traps, behind the speakers, and back wall spots did the job. I have carpeted floor and a lot of furniture, so that may be why treating the other spots wasn't necessary. Plus, my D2 has a really good auto EQ (ARC) system that manages the bass very well.