Just so you know, a GFCI won't protect you from getting shocked to death by your amp. There's enough energy stored in the amp when it's off to kill you, so if it doesn't have a path to ground it just stays stored in the amp. The GFCI is there to stop current leakage, but the amp can rip current through your body before the GFCI trips. Think of all the capacitors in the amp as a big-ol bunch of batteries. BTW, DC volts hurt worse (are more deadly) than equivalent AC volts, and capacitors store DC voltage.