After a couple of disappointments trying to source Servo15's on the Forum I finally managed to get hold of couple of Servo15a's. These are a 600W version of the Servo15 I didn't actually know about until I saw these advertised. I'd previously been warned not to buy a Servo15 without the X-30 controller so I put a "WANTED" ad. that turned into a little Do I need one?" debate. From what I've read the X-30 allows you to change the phase and vary the crossover frequency. Someone suggested the BFD (Behringer Feedback Destroyer) would be a beteer bet for me. So here goes.... My system is almost entirley for movies. I'm in a huge (12,500 cubic/ft) accoustically challenging (but great sounding) room. It is my intention to use the 2 Servo15s together. I have a Lexicon MC-1 with all speakers set to small (80). I'm currently double stacking them in the left front corner. Do I need an X-30? Do I need a BFD? Do they in anyway duplicate the same job? Can they be used together. Having only just got the subs I've not yet worked out the best placement position but I will try and get another pair of the later to place 2 at the front and at the rear of the room. Also.. I've put my Rel Strata II up for sale on the Forum. Should someone not buy it can this smaller sub be a further benefit to my system? Thanks for any help/advice, Mark.