The subs are set to max trim of -12 simply because the subs are playing too loud. To properly set up your two subs you will need to turn them down and level-match them as per the Audyssey Setup Guide, then rerun autosetup. Before you do that, if you have some flexibility in placement, the fact that you have two subs offers an opportunity to use sub placement to smooth the in-room bass response. One of the lessons I've learned using 2 subs irt music is that unlike film, it's not LF extension or overall volume that's the point. Especially if you have no bass traps, listening or better yet measuring to obtain a smooth bass response with the subs may improve overall SQ because of the acoustic advantage derived from careful placement to counteract room modes. This applies regardless of the capability of the mains as those are placed in the room to optimize imaging and soundstage. Using a crossover of 80 or so and including the subs has other advantages such as the increased Audyssey filter power in sub channel and off loading work from the mains and the amp that drives the mains. We can talk more about sub placement if you're interested.
As to MC mixes, you're of course quite correct that some mixes are more "in the band" with instruments placed in surrounds, far off the usual front stage and/or are specifically designed to emphasize surround effects (Pink Floyd DSOTM). Some essentially add just room ambiance in the surrounds. Some discs (2L Divertimenti) even offer a choice of surround mixes, "stage" or "audience". In that case I often prefer audience mix for most classical music.
As to MC music, placement and type of surround speaker is different for film vs music. Music benefits from timbre-matched direct-firing speakers placed at close to ear level and at 110-120 degrees off centerline. One can adjust a MC mix to some extent by using the fader control, and I sometimes prefer to turn down the CC a bit.
With your dedicated analog system, using the upgraded dedicated stereo outs of the Oppo will no doubt offer a distinct advantage over the std Oppo DAC. The disadvantage is that system does not have the benefit of Audyssey, especially if your room is untreated.
For audiophile/very critical music listeners, I recommend the latest improvement in Audyssey, MultEQXT32 (as in the processor I have, the Denon AVR A100/4311). XT32 does a better job as it applies correction where it's most needed and leaves the rest alone. I also use the Audyssey Pro kit which brings a more accurate mic and more powerful processing to bear. That combo is is a more powerful, more sophisticated and more accurate DSP RC system.
Yes, I still like playing with Dalis.