I think you should get a 6 channel AMP from ADA. Their model
PTM-6150 get high appraise from Home Theater Magazine and other Bristish magazine. It get the same rating as Bryston 9B in Bristish magazine. Its street price can be under $2000. You can research this amp in e-coustics.com and manufacturer web site ada-usa.com The six channel amp can power you rear channel (THX-EX) without purchase additional amplifier.
PTM-6150 get high appraise from Home Theater Magazine and other Bristish magazine. It get the same rating as Bryston 9B in Bristish magazine. Its street price can be under $2000. You can research this amp in e-coustics.com and manufacturer web site ada-usa.com The six channel amp can power you rear channel (THX-EX) without purchase additional amplifier.