I was going to suggest using an M3 or dual M3's(one above and one below the display) as a center to match up to the M50's.
If the M60's were possible why not the M80s and have the best midrange out of the M22 and even better bass response? The M22 sub combo lacks a little upper bass feel that the M80s bring to the equation. I went this very same route, started with M22, ordered M60s found the M60s lacking a little in the midrange compared to the M22 and then went for the M80s after some more comparison listening.
