Welcome to ASR. I believe I've read many of your very informative posts on AVS re: the RZ50.Just joined the forums, mostly read thru the 28 pages for this thread. Just wanted to key in with my personal experience of the RZ-50.
I got it soon after it came out, it was the only AVR that really had everything I wanted/needed (except Auro 3d) I have a smaller room but with an open floor plan so the livingroom is open to the kitchen and hallway, and then that's open to other parts of the house.
I decided to pair the RZ-50 with 4x Monoprice THX-365T and a THX-365C, and 4x SVS Prime Elevation speakers.
The speakers are rated as 4ohm for all 5 of my base layer. So I am powering 9 channels all from the AVR.
I AM offloading the AVR quite a bit by not running full range speakers, I have them set to small crossed at 70hz.
Bass duty going to a MiniDSP 2x4HD and 4x15" Monolith subs.
I have taken a DB meter and cranked it up to reference with more room to go before I maxed out my volume, and I listen rather "enthusiastically" sometimes. So far with months of operation I have not had any sort of protection mode kick in, or noticed any issues at all.
So while one persons experience cant be definitive, I wanted to at-least share that in the case of how I have things configured, even with 4ohm speakers this AVR has been solid, and preformed up to and beyond my expectations.
I do have some amps laying around that I thought about trying out "just for fun" but I am not expecting to really get any gains from doing this, it's more "for science".