The first thing to do is figure out the voltage output and amperage of each wall wart. If you were lucky enough to have a bunch of 9 volt power supplies, a guitarist's pedal board power supply might be the ticket. Seems like most audio related wall warts are 12 volt though. Something like this can replace four power supplies:
http://www.bkprecision.com/products/power-supplies/1520-universal-power-supply.html
http://www.bkprecision.com/products/power-supplies/1520-universal-power-supply.html