I have had Eminence MS-12/EV's in mine and currently have MC-90/EV mix. I wish I would have kept the 2 Eminence MS-12's, but I sold them before I really knew what I had.
I tried the top section of my cab off for a while and really didn't like it. I just had trouble getting the tones I was looking for on the mark IV, the bass just seemed to disappear. I recently put the top back panel back on and the tones I was looking for came back. I got this cab from Mctallica1, so you can ask him what he thought about it if he remembers, its been a few years though.
On a different note, Dave, why are you selling your halfback cabs? Have you moved to the marshall side permanently?