I had this situation. My couch was right up against the back wall with about a 9 foot throw to the front speakers/display. On either side of the couch I had tall shelves with surrounds on top. I tried a couple placements for the 2 surrounds which worked. My favorite was aiming the 2 surrounds so that they were firing diagonally forwards. In other words, the right surround faced the left front and vice versa. This sounded the best to me. Firing them both at me from the sides called too much attention to the surrounds.
Also, I used a sound panel behind the couch to minimize reflection - this helped but may not be practical to everyone. The surround set up I had worked without the panel though. The trick is to have the front 3 speakers at EAR level! This means that no speaker is really above the top of the couch, which means, minimal reflection from the rear wall. Again, surrounds worked best in the diagonal-forwards position. The weren't firing straight at me, but instead sounded more diffused. Firing them back at rear wall as some sugest just didn't work for me.