I have a Sony STR-DG720 AV Receiver which as an RCA male plug outlet for the subwoofer. My subwoofer, part of a DAV-FX10 home theatre system, ( I ditched the player for the new receiver but kept the speakers) has speaker wire connections. As it is not powered will I have to buy a subwoofer that is powered or is there some other way to connect the receiver.