I might have a go at recording it turned up a bit louder tomorrow if I get the chance, it can get pretty loud, I have only tried turning it up to about the 11 o clock position on both channel master volumes, been feeling a bit scared to turn it up past the 12 o clock position, it's a 100 Watt Valve amp after all, and some 100 Watt Valve amps can get ear-piercingly loud, my mate's Peavey Triumph is only a 60 Watt Valve amp but it easily keeps up with my Marshall.
I reckon my Marshall really needs to be plugged into a 4 X 12 Speaker cab to sound it's best, trouble is, my mate reckons I should only get a 2 X 12 Speaker cab for it, since it'll be less awkward to carry up and down one flight of stairs.