OK, that receiver will be great for cranking in stereo. I don't know about movies because I can't find detailed info.
Don't spend any more money until you have a chance to develop an appreciation for what you already have. One suggestion is to try playing your M5s without and with the Klipsch. You may have to dial down the M5 bass. Try to bring them away from front and side walls. Also try the AccuEQ.
Excellent choice on the M5s. You'll really enjoy them except maybe the first 30 hours. They take about that long to ripen unless someone at Axiom is planning to party with them before they get shipped. What finish? What surrounds?
BTW, the 160 is awesome!
