I have one 12V (14V) automotive light running off of a 12V black "wall wart" AC->DC transformer (pic below) off of an old electric piano. I have run them off of the variable kind Radio Shack sells, which will output 1.5, 3, 4.5, 6, 7.5, 9, and 12 volts. I've run it at both the 12 and 9 setting. 9 is about perfect for the room I have my cocktail cab in. Plenty bright and less hot. These lights were designed to be visible from 100 feet away in the fog @ 12V, so even at the 6V setting, they're still pretty bright in a room.
I would think that if you got a hefty enough 9-14.5 volt transformer out of a printer junk pile, you'd be good to go for 10 bulbs.
No warranty, of course
