Sam, as Tom mentioned, any sub which has speaker level input and output terminals(most of them)can make that connection. The input terminals are a connection into the sub amp plus a straight through connection(no processing or power loss)to the output terminals and then out to the connected main speakers.
I assume that you also saw from the manual that since the 507 amplifier has five output channels, that if you use two of them to power the Zone 2 speakers then you can't simultaneously have the surrounds powered in the main system. The Zone 2 setting would have to be turned off.
