I don't have any experience with Marshall cabs but used a 2x12 rectifier cab with an ROV combo.
When you say "halfway up" are you referring to the 12 O'clock position? That is the sweet spot and I don't think the rectifier series are really designed to be pushed past this point.
My 2ch DR at this position w/ the master, the loop active master on and send at 100% was noticibly louder and punchier than my ROV.
I used to crank the ROV in an auditorium that I have access too. The DR at this level, in this auditorium, was a noticible increase in headroom. I do not recall the ROV vibrating the whole auditorium like the DR did. I was using a 4x12 and 2x12 rectifier cab and that could have contributing to the vibration.
I now lower the volume on the DR in that Auditorium with the send level on the back of the amp and leave the master and loop active master at 12 o'clock and only plan on using the 2x12. Those 4x12's sure are heavy!
The auditorium is in a corporate office building so even on weekends there are employees present. I can't push the DR at louder levels for fear of loosing access to the space. 50w to 100w is not twice as loud but my brother and I definitely noticed a difference.
The ROV is great amp and I'm sure the Single Recto is too.
My 2cents though I like the additional options that the DR offers ie El34's, Tube rectification, bold/spongy, loop assignable etc
