No, I haven't and thanks for the suggestion...depending on where my odyssey takes me, I will keep it in mind for a future audition.
I have just added a PS Audio PerfectWave DAC to my system on Friday and, FLAC files played on Sonos through the PWD with the Onkyo set on "Pure Audio" setting (no processing and all video circuits and display turn off) sound great and I think I've solved the issue to a large degree. Out of the box this DAC is wonderful -- great soundstage, imaging that is spot on and a sense of depth in the sound that I've never heard before in my room...a big improvement over the Cullen modded PS Audio DL-III that I tried previously (it is a great sounding DAC too). I'm not sure if I bought the "break-in" theory for electronics previously, but owners of this DAC say that after 100 hours or so of use it really blossoms, so I'm running it continuously and playing some of the same tunes when I "audition" it again during the break-in and, I have to say, that it is sounding better each time and my system is really sounding musical again.
Back to EQ as someone pointed out, EQ isn't where you should start...room treatment is the first step and my room has had professional sound treatments installed. I also have a couple of subs in my system...don't know if that is enough to prevent the nodes that were brought up, but two is all my room can handle.
As for EQ and the processor, the Onkyo adds Audyssey processing when set on stereo (which also adds in the subs). The soundstage gets even broader (compared to Pure Audio) when on this setting, but the imaging gets less focused too...kind of like on boomboxes that have the "expanded stereo" setting. I definitely prefer running the processor on "pure audio" when listening to music. I can turn off Audyssey when it is set on "stereo" and it does improve the imaging and the overall sound, but it doesn't sound as good as when listening on "pure audio".
Frankly, I didn't have this issue with the stand alone Audyssey Sound Equalizer and my Integra Research RDC-7. I assume that is a combination of the DACs and components in both units...additionally the Audyssey SE has much greater processing power than the Audyssey that is built in to any processor or receiver. Listening to my FLAC files via Sonos with the RDC-7 doing the D/A conversion and with the SE in the loop, there was no fatigue, imaging & soundstage was great, etc. Like I said in an earlier post, Audyssey was calibrated by the same guy in both cases, so I have to assume that it is the lower processing power of the Audyssey chip in the Onkyo and the lower cost of the Onkyo compared to the combo that it replaced that is the issue. (the RDC-7/SE combo was about $7K versus $2K for the Onkyo...silly me thinking I'd get the same performance...that's what I get for "listening" to the posts on some other forums that shall remain nameless).
The current 2-channel sound with the PWD exceeds the RDC-7/SE combo to a large extent,(the Onkyo wins on video processing/switching and on surround sound) but when listening to "pure audio" my subs aren't in the loop and my Paradigm Active 20's aren't full range. While most music doesn't go down to 20Hz, I do miss the low end reinforcement that they provide. Also, at the price point of this processor, the analog inputs probably aren't the best and I'm not hearing all of what the PWD can do. My RDC-7 was a great 2-channel preamp both on digital and analog, so the Onkyo is a step down from where I was for 2-channel.
My solution will be to get a Wyred4Sound STP SE preamp that I will use for two channel listening (it has a HT bypass) and I can then run the mains and subs when listening to music. 6moons just had a great review on this preamp and I'm very excited about putting in the system in the near future. We'll see where I go after I plug that in...new speakers, more room treatments, another Audyssey SE...who knows. The funny thing is the total cost of the Onkyo/W4S/PWD is going to be in the $7K range too...just like my RDC7/SE combo...
So, back to the original subject of this thread, in my experience with processors (and with DACs), to these ears there is definitely a difference and it can't be explained just by not having matched levels. I do believe that you get what you pay for in most cases.
As with all things, there prolly gets to be a point of diminishing returns (where that point happens is probably different for all of us) and if you can hear a difference and can afford it, go with the best equipment your money will buy. Conversely, if a person can't hear a difference, then that's cool, go with the more economical stuff...either way it is your money.