I've never heard the 581. Also, as noted but not explained, my 860 is modified, fairly significantly, by Steve Huntley at Great Northern Sound, who used to work at Wadia and before that ARC. He's well-known for his Wadia mods, and I was amazed at the musicality of the modded version. The unmoded version (which I used for a couple of years) was overly concerned with treble, and detail, detail, detail, and was fatiguig. The GNSC version has much improved tonal balance and a very smooth top, though it is still quite detailed. But it still has some positive Wadia characteristics, including rock solid bottom end (even more so, really) and, like I say, great detail (but smoother). I mean to say here that there is a family resemblance between the unmodded 860 and the GNSC 860, but the GNSC 860 is (for me) much more pleasant to listen to.
I did not like the unmodded 860 straight into my amp generally, although on a very few of the exact right CDs, it was stunning. It's just that on quite a few CD's, I heard more than I wanted to know. I've never tried the GNSC 860 straight in.
The EMM is less dynamic than the GNSC 860. It actually has somewhat more detail. The soundstage seems further back from the speakers and is a bit wider, I'd say. Particularly with orchestral music, the extraction of detail from redbook CD's is remarkable.