Hi,
I have the TX-NR905, which I assume is what you're referring to.
I would never question it's strength of amplification but I certainly questioned it's online finctionality and it's DSP's/Decoders.
Running a Kef THX Reference 7.2 system in the main room and Boston Outdoors on the patio. Stereo only on the patio.
In the main room, I could change to any of the surround modes and would hear little to absolutely no difference in tone/surround effects, with the single exception being Multi Channel Stereo but that's practically a given.
Previous to that, I had a Marantz SR4300 and then a SR5500, in a different house but with same speakers. There was a noticeable difference in sound when I switched surround formats/DSP's every time and it was also a very competent performer with music.
Being honest, I've been itching to get back to a Marantz almost from the time I bought the Onkyo but I couldn't resist the feature list and power rating of it at the time, considering my 4Ohm speakers and the price it was going for.
I have recently swapped it out for a Denon AVR-X4000 and am quite delighted with the new model.
It's quite a bit lighter and a little shorter than the 905, though I certainly wouldn't consider it lightweight.
The sound is a little higher in the treble and, with Audyssey engaged, much lighter in the bass. However once I disengage Audyssey, I have almost all my bass returned and can tweak the subs to make it deliver more but have not felt the need.
When I change the Surround/DSP, there is a palpable difference in the room.
The stereo on the patio could do with a little more bass but I am only fine tuning that as the weather improves.
The network functions of Media Server and Internet radio are brilliant, especially noticeable being the difference when stepping up from MP3 to FLAC/High Bitrate radio stations.
I believe the Denon X4000 is very similar to the Marantz SR7007 mentioned above.
If you're into movies, go for the Denon but if you're into music, then the Marantz will probably suit more.
Or if you want another NR905, I'll be selling mine for €600 shortly
Barry.