And, not having heard what good surround processing can do for your SACD, you'll probably be fine with what you've got

UGGG I can’t do this right now but one thought. Did I speed read all this thread correctly. You’d prefer a lower resolution 2-channel CD processed via L7 VS potential 5.1 discreet channels at higher resolution. Although the quality of the HR discs and quantity placed in each channel IS all over the map currently.
(and do you prefer DD over DTS?) (or just DD vs the spawn?!) Eki! our ears are different. I do like your MC12!
Logic 7 is VERY good ….but its not that good!