So I've just had another rehearsal in a studio that has a V4B with SVT810AV as backline. I'm not sure if there's something wrong with the V4B but it just lacks any presence with my CS 61J. So I took my Micro VR head and sat it on the 810. I had to back the bass control off a little as there was too much low end but the sound was huge and classic Ampeg. Previously I've only used my micro VR at home with my SVT210AV but with the 810 it totally killed the lacklustre V4B. Apparently the micro VR puts out 260 watts into a 4 ohm cab. The volume and tone from this combination is a revelation to me.