Congratulation and welcome to 'MY FAVORITE AMP'!! I can certainly understand the 'not loud enough' comments that some folks have, but for myself and others, it is plenty...
If you look at coreyfyfe's picture of the early '70s one, well that is where my volume was set for last night's gig, (input pad was set for -6db)... This is with a passive P into a Musicman HD-115 single 15 cab, (Treble and bass at 2 o'clock, mid switch at 1000 with the knob at 12 o'clock)... Two guitars, harp, and fairly loud drummer and it sat well...
For me, the effective volume limits out between the second notch and straight up, (10 o'clock and 12 o'clock), but I never need to go there anyway...
With an efficient 2X15 cab, it could go from over-the-top grind to a pretty modern sound. The Musicman cab is pretty efficient, but old school sounding, which is what I am going for. I would love to score a matching V4 4X12 cab to replicate the rig I was using in the early eighties... I'll keep looking, (and lusting after johnk_10's rigs!!!)
-robert