I recently bought Onkyo TX-NR676 installed 5 ceiling speakers 3 on front Acoustic R191 and 2 rear for surround Pyle PDIC60 so my question is I need to add a subwoofer to my receiver the receiver has 2 RCA On the back 1 says subwoofer and another says subwoofer PRE out. now I have a subwoofer...