I have a Sony DA5es with a 5.1 setup. However, I would like to hook up an amplifier to it so that I can attach 2 surround back speakers. The sony is a 6ch amp for a 6.1 setup, but I would like to add 2 speakers instead of one. I would like to know if I can use any amp/receiver to accomplish this additional task. Plus, what happens when I adjust the volume at the sony amp? Will the two other speakers increase/decrease in vol accordingly, or will I have to adjust them seperately with the add on amp? I am confused about this setup and would appreciate someone to explain how it is done. Thanks very much.