Originally Posted by Primakurtz
As a backup, consider the Mesa M3. Cheaper and lighter than the 6 and 9, with gobs of power and volume.
Wouldn't hurt to look at the M-Pulse 360/600's as well. Great amps, with a good DI. Worst case scenario should the Buster crap out, you just DI to the FOH and you'd be set for the rest of the show. I don't think you'd really need the power of the M9 as a backup, but if you can swing it, why not?