I'm not saying the extra rear surrounds are completely worthless but I wouldn't lose much sleep over them either. In my previous HT room I had some direct radiating speakers for the 6/7 channels and in my currently HT I have some old QS4's that I'm using.
The rooms are different and my situation was similar to solardadd's. I would give the same recommendation but I would also add that if you already have some speakers to use back there, use them and spend your money on other components. I have yet to find much content that makes those channels necessary and yes I always enable PLIIx/NEO:6 for 5.1 material.
