Pete, it was the GK MB500 amp here:
http://www.gallien-krueger.com/products_mb.html
Not 400 Watts, 500 (@4 ohms); Not 5 pounds, but 3 pounds 12 ounces.
I'm thinking with 2 Avatar 112s, one of these, a samsamp pedal and a floor tuner... I would have no money, but the most portable setup ever that's still loud.