Hi cofalt,
I would entirely endorse JohnK's views on the essential similarity of receiver/amplifier "sound", so long as the unit is not driven into clipping and has a flat measured frequency response.
However, I would point out that some of the alleged audio differences heard by consumers in stores could in part be attributed to small variations in the tone-control circuits between different brands when they are left in the circuit.
If you measure frequency response of A/V receivers with the tone-control circuits engaged and "Off", there are measurable variations through the midrange "hinge points" and sometimes these are audible, because the variations may be up to 2 dB. Our ears are especially acute in detecting tiny variations in the midrange.
Apart from the many other variables in store auditions, the aforementioned could account for some of the differences heard.
The reason that you don't get much feedback on Onkyo units is that I tend not to recommend them because, unlike the Denons and H/Ks, many Onkyo models will not drive 4-ohm loads without invoking current limiting, protection-circutiry shut-down, or overheating.
That doesn't matter if you are driving 8- or 6-ohm speakers, but with the 4-ohm Axiom M80s, it does matter, and customer feedback has shown that Onkyos (generally) won't drive them. Even the entry-level Denons and H/Ks have no problems driving 4-ohm loads.
Regards,
