your in the right area, I'd maybe have a bit more of the mids in there, I'm presuming your on the lead channel there. You're probably over complicating things, especially using the 1960 cab, that's going to phase things up quite nicely (in a bad way). Try 1 Sm57 (not beta) at the centre of cone, an inch away from the grill cloth. Try this on each speaker, then compare, find your favourite speaker, then move it about an inch -if that, off centre to try and get rid of that high 10k fizz, maybe filter 60hz down and 12 k upwards out. If it's sounds great in the room, it has to be something your doing later. Nothing drastic was done to the EC gtrs in the mix. I think we used the rhythm channel though, with Tube Screamer, though that doesnt sound like the problem, as I use the lead channel also some times.