I've taken the surround volume levels down from the recommended surround levels that Audessey came up
Interesting, my X2500H with Audyssey XT (non-32) sets the rear channels too low. Maybe because I'm in a less than perfect room, with both rears on the wall, and one of them in a corner. Maybe it sees extra bass loading from the corner and adjusts the global level instead of a high pass filter.
What I've done is take a mono white noise or pink noise signal (both should work, pink is more pleasant to the ear) and played it in the multi-channel stereo mode, so that all the speakers are playing the same signal, but with levels, delays and EQ applied. Then I have adjusted the levels so that I feel myself evenly surrounded and submersed into the sound, with nothing sticking out. I had to correct quite a bit (3-5 dB) on one of the back and one of the front channels compared to the Audyssey XT auto-calibration. Not sure why, it's suspicious, but I did like the result post manual adjustment.
Yes, I do, I have a 1970s decoder and play SQ and QS encoded LPs in what's now referred to as 4.0.
I don't have the room for a proper 5.1 installation, nor have most of the LPs I play been released in 5.1 format, so stick to my 1970s Quadraphonic playback.
S
You can ditch the center channel with no regrets. Just get any 5.1 AVR, even an older one with Dolby Pro Logic, hook up to your 4.0 system, run the calibration, and you can listen to all stereo music (both digital and analog) in upmixed 4.0 mode. A calibration mic is also not strictly required, it's not hard to measure distances with a ruler / laser and set levels by ear, but you won't get room and speaker correction, which I like very much.