It sounds wonderful, but PJB stuff isn't the loudest unless you add cabs.
I think the Six Pack only puts out 190-odd watts into the combo so you'd really need to add the right impedance cab to make the most of the M500 head that's in it. That, of course, makes having such a heavy combo in the first place a bit redundant, at least it does to me!
I'd suggest you look at the manual and see what the cab configurations and power handling do, and whether you can get the right setup for you.
Cheers
Gareth