Hi Dennis,
This has been well-covered by most everyone here, but it all began some years ago when Axiom got reports of certain brands of AV receivers shutting down (or overheating or going into "current limiting", which limits output power into low impedances) when driving the Axiom 4-ohm M80 tower speakers.
That's when at Axiom, we went through a number of brands at our factory (and owned by myself and Axiom colleagues) to determine which models would drive the M80s and which ones would not. The winners were H/K, Denon, Rotel, Outlaw Audio, Arcam, and B&K.
The losers at that time included Onkyo, Yamaha, Pioneer, Kenwood, Sony, etc.
I also avoided recommending some AV receiver brands that in my experience as an editor of AV magazines for many years, had quality control problems in the past (Onkyo, NAD, Kenwood) or had been disappointing in one respect or another (Sony).
As the years have passed, some brands like Pioneer have introduced certain models with MOSFET output transistors (the VSX-1015) which, although inexpensive ($499) will drive the 4-ohm M80s. That's true as well of entry-level models from Denon and H/K.
I can't help you out on the Pioneer Elite models, but any that advertise MOSFET output sections should not have any trouble driving lower impedances. There is a more recent Pioneer (the 1016) which has HDMI switching but does NOT have the MOSFET output section, so don't get that one if you plan on using 4-ohm speakers.
