Hi, Finally i have assembled my home theater system with MA sliver serise of speakers ( S8, SLCR, S1). Now some friends told me to put instead of S1 SFX speakers. They think that i will get better movie effect with it. My question is can I keep S1 in my configuration system or i must buy SFX speakers? Also can i leave S1 for 7.1 configuration of speakers? And last one, is that so necessary to buy that SFX speakers to replace S1 on REAR position?