As seems usual for Onkyo, the TX-SR605 showed just how technically accomplished mass-produced electronics can be today, with perfectly flat frequency response and perfect D/A linearity to -90 dB (and beyond). Both are as good results as I've measured, and while my memory isn't infallible, I believe this to be the first time these two particular aces have been drawn by the same unit.
The Onkyo TX-SR804's overall performance was fairly typical of mid-range receivers today, which is to say astonishingly good in most respects: Noise, distortion, and frequency response were generally very good.
I've come to expect stellar bench results from high-echelon Onkyos (and lower-echelon ones, too, usually), and I got them. Noise and distortion measurements were uniformly state of the art. Frequency response was excellent as well, though the TX-SR875 exhibited a very small rolloff, of about 0.5 dB per octave, above about 10 kHz in all playback modes.
Pioneer's latest A/V receiver produced uniformly excellent bench results: linearity and S/N were close to perfect on both PCM and Dolby Digital signals, while distortion and frequency response were nearly as good (the latter, in particular, on 96/24 PCM).
The Sony STR-DA5200ES presented no surprises. Power was generous in all tests save all-channels-driven, where the receiver topped out at 66 watts all around; note that this is only 4 or 5 dB less than from the most powerful receivers we've tested on the demanding all-channels-driven test.
I encountered no glitches or surprises while testing the Sunfire Theater Grand Receiver 3. Power output was consistently among the highest I have measured from a multichannel receiver, and its 165 watts (22.2 dBW) per channel with 5 channels driven represents a clear benchmark for the category (3 to 4 dB greater than flagship receivers from many other manufacturers achieve).