Hmm. How much throw do you need? In other words, how far do you want your amp(s) to move? Most actuators in car doors travel 1-2" (AFAIK) so I don't think you will find many at the traditional car stereo type stores.
Are all of your amps in a row? What ab out connecting them together in the back and then sliding them out with a motor. You can use a cam so that if the motor stays on it will cotinually slide the amps in and out. Actuators would slide the amps out...but it would be in one explosive move.