Cab education and recommendations required

Sassafras

Also, I don't like closed back cabs and most of the 4x12s I've encountered have been closed back.

Beexter

I use an MJW 1x12 with my Mesa Express and it's bloomin marvellous. Speaker is an Eminence Wizard 

imalrightjack

Finally ended up with a second-hand Mesa Express 19 cabinet.  Sounds terrific with the Mark V: 25 and finally makes it sound like the amp I thought it should be.  Very happy.