I've got a pioneer vsx859 receiver and celestion speakers+sub. I'd like to add in the extra 2 rears i.e go from a 5.1 set up to 7.1 The manual talks about wiring in a 2nd power amp to drive these rears. Could I use my old Marantz pm44se or my spare Rotel 931 amp? They are integrated amps so not sure if this is possible. Any help appreciated.