also the lack of mids makes it seem more gainy as well. try setting up an amp with moderate gain, crank the mids and play. then scoop them and play. it seems like there is a lot more gain, but there really isnt.
and maybe the volume being so high has something to do with it? from what i understand they slaved the II's out to a Marshall as a poweramp. maybe that and the volume has something to do with it?
I've never played a 2C+ but my mark III blue stripe has quite a bit of gain with vol 1 on 7.5 and my lead drive on about 6, I would guess that would equate to similar gain levels as seen in the pics. Also given the time period there's a good chance that those boogies were loaded with the older chinese 12ax7's, not the most toneful tubes but they did distort and crunch big time.
...but where the fuck is all of the gain coming from? James says that he didnt need distortion pedals with the Boogie amps...yet when I look at his settings, there is almost no gain