Hey mate,
The 90's Model T generally goes for around $1000 on E-bay and in classifieds, so I think you're getting a pretty fair deal. If you consider that you're paying a grand for the head, then you're basically getting two 4x12's for $500, and considering that those cabs are loaded with G1275 Celestions, that's a bargain. You'd really be hard pressed to find a lower price on that stack.
I can't help with the volume issue. If you're concerned, get it checked out by a tech before dropping your hard earned cash. Any good seller would accommodate you on that. All in all though, setting aside any comparison to the original Model T, the 90's Model T is a crushingly loud tone monster, and I think you'll be very happy with it.
- James