I would check your connections at the amp first... especially if it is an intermittant problem...
Also check your RCA leads are also in properly and that they have no breaks in them..... if they are stressed at the headunit it doesn't take long to cause problems.
Off my little jap battery I am running 2 amps, tv, 2 subs, front components and rears. It wouldn't be the battery as you would notice other things such as dull headlights etc.