Now got my amp and DVD player, so wish to access 6.1 surround sound. Should I do this my purchasing just another centre? Or should i take advantage of 7.1 and purchase another set of stereo speakers? i can easy install another centre right behind my listening position, but how do I install an additional set of stereo rears?? The existing rears, are firing just behind me right in the corner of the room - the seating postion is hard up against the rear wall. But I do have a high window sill being to sit a centre speaker. I could fit two rears on there as well - do they just fire over the listenign position????