I am in a quandry as to where to place my QS8's...

Since my listening couch sits on the back wall I have no way to get the speakers any distance behind me. I can get them 1-3 feet above my ears and 3 feet to the side, but I am sitting on the same 16wx20h ft. wall as the speakers.

On the other hand, I could place them up on the side walls, but again I will not be able to get them behind me at all. In this position, they also will be located in the corners where the side walls meet the back wall.

So the question is: Back wall unobstructed, or side walls obstructed on one side each?

Supe, I suppose the first point should be why with a 19' long room the couch has to be all the way up against he back wall. In any case, you've probably read that in a 5.1 setup the surrounds should be directly to the side, or preferably, a short distance further back from the listening area. In your situation I'd think that mounting the QS8s on the back wall, but separated more than you mention, say about 12', so that the outer QS8 tweeters would bounce off the side walls, should work well.