I admit I am a bit of an audio noob. I have only recently gotten into surround sound, and at that I am only dealing with a Vizio 5.1 sound bar (yeah, I know, but the room, the wiring, the wife factor...gotta do whatcha gotta do). And I have struggled with my rear speakers because they are often barely audible. If I feed PCM, they are louder, fuller, noticeable. But, if I bitstream, I need to crank the surround volume (rear speaker volume) up to max to get a reasonable volume out of them.
As for placement, I had them behind the couch and slightly out to the side, but facing towards the middle of the couch. But just recently, I put them off to the side of the couch by a couple of feet, sitting slightly behind the ear/head position and angled at head position, not pointed at the center of the couch. It has made a big difference. I don't know if it's correct, and I will probably move them again, but they sound good so far.