I am not much of a writer but I can elaborate on the differences I noticed. Before the 840c I was using a Harmon Kardon DVD25 as a transport and coverting at the Behringer DEQ2496. For me, the DEQ was/is an excellent tool for 3 reasons. I could correct my room, utilize it's dacs, and tame any nasty harshness inherant in female vocals. The biggest problem was by attenuating frequencies between 1-6khz, naturally, I was losing information from guitars, piano, snares, cymbals etc.
Here is what I have noticed, so far, with the 840c. I can leave my EQ flat, with the exception of a 5-6db attenuation at around 60hz.(room issue) All my harshness is gone, even with cds that I wouldn't listen to before, yet the increase in detail is incredible. The soundstage has widened by a couple feet or so, the separation of instruments has improved dramatically, I have a much larger sweetspot, There is an added fluidity to the midrange, the high frequencies have been extended and seem to dissolve into nothingness around you. (not bad for a horn)
From what I have observed in this hobby systems can be dark and lifeless to super clean and detailed to the point of being clinical with no musicality. I wouldn't want any more detail for fear of sacrificing musicality. For once, I have the best of both worlds. I feel I am balanced firmly...deadcenter.
I am not an audiophile and probably know less than 99% of the people here. The CA840c may or may not work for you, who knows? In my room, with my gear, to my ears it's superb!!!