[noodles]

Eh, I really don't like open back cabs of any kind. They are great for cleans, but get really boomy and indistinct when you pile on the gain. That's a cool vibe for some leads, but not for precision rhythm work.

I'm not sure a Mark IV head would sound that good through only one speaker. The Mark IV combo is built with that purpose in mind, and will also be much better at it. I would want at least a 2x12 for that amp.

Not that I want to discourage someone from buying Mesa, but Vader makes a good cab, too. Necrophagist was plugging Engl SE heads into Vader 4x12 cabs, and they sounded amazing. Unless you can find a Mesa Recto 2x12 for less than the Vader, go with the Vader.