My parents bought me the Pioneer VSX-D812 receiver for my birthday, I havent yet received it because it's on lay-by however I downloaded the online manual and had a look through it. On the back panel, where the speaker terminals are, there are Front L/R, Middle, Surround Back L/R, Surround L/R and another set of Front L/R. My question is, Why are there two sets of Front L/R? I have also noticed A next to the first set of speaker terminals, and B next to the second set of Front L/R terminals. Is it possible to have two sets of front L/R speakers and switch between them? Thank you.