Thanks for your reply. Currently I am running STS with LFE, the crossover is set by Audyssey to 40Hz. I also tried them with THX crossover of 80Hz and as full band without internal subs. The result is the same. The scene is flat and there is no good separation between different instruments. Piano doesn't sound like a piano sitting in the same room. Behind a closed door? Maybe...
I can't find "large" or "small" settings in Onkyo 807. Am I missing something?
The thing is that I have connected my old Techincs speakers as surrounds to the same receiver and if I run "all channel stereo" I defintely get much more information from surrounds than from STS fronts.