Okay so I was installing an amp for my speakers. Originally I was gonna put a 450 watt sony, but we ran into some problems.... needless to say, me and my friends have swapped out every single component of this system. Stereo, power wire, ground wire, ground, RCA cables, even tried different amps nothing fixes the problem. The amp still turns off when the volume goes past 25 (out of 50). However, I can get it above 25 when i am revving the engine at around 4,000. The ground is getting a constant 12 volt. Here are the specs of the system:

Sony Xplod stereo
Pyle 12 guage remote wire
Rockford Fosgate 8 guage power wire with 2 60 amp fuses (OFC)
Random OFC ground wire
Home audio RCA cables
Kicker ZX 350.4

Im thinking its the battery or the alternator, but what else could it be? Every single wire is fine and the amp has been bench tested in multiple cars and in a home audio environment.