A couple days ago, my amps stopped turning on... so I figure my remote lead came loose from the relay or something. Well, last night I checked everything with a multimeter. My remote turn-on lead is fine because I'm getting 12V when the HU is on. When I checked the power cables at the amps & capacitor, I'm only getting 6 or 7 volts. I figured I'd ask before I rip out my system, as it's all custom... what do you think? Grounds? Any suggestions are welcome.

You checked all of your in-line fuses at the battery right? Sounds like you are only reading the left over voltage at the caps..def check your grounds, be sure they are tight and on bare metal..

check that ground