Thanks John,
I assume the hole is less likely to occur due to the QS8 trailing of to -9dB@65Hz. As for using the QS8 as a center back, I've always used two center back speakers to counter the psychoacoustic effect. I've tried it with one and it's always seemed like the sounds where coming from the front center channel just as you described.
You and BrenR both answered the one or two QS8 question. I assumed that due to the dispertion of the QS8 only one center back would be necessary, but like you said DPLIIx can seperate the 6th and 7th channel. My room works really well with two direct radiating back speakers, but I think two QS8 may be a bit much in a room thats 13' wide.
