amps in protection

What I got... 2 ma audio hk 1398 amps 2- 10" mtx 9500 4 ohm dvc subs wired at 2 ohms.  0 ga ran to back to distr block 4 ga to amps which are bridged to a 2 ohm mono load, Alpine deck and changer.   My problem is when I turn up the volume the amps will go into protection for a few seconds then will resume, my thought is that the voltage is droping too low causing this.  voltage goes from 13 volts to 10 volts.  My guess is I will need to add a battery?  Does anyone know at what voltage the amp is set at to go into protection.  All is in a fully loaded '06 trailblazer ext.  I am new but have been looking a long time.  I will put pics of my set up soon.  Any help will be awesome.

Oh boy $$$.  I couldn't find any on ebay for my year blazer.  What size (and where) should I get?  My amps combine for a total 320 amps,  I also have the dvd, heated seats and all.  I planned on doing the big 3 upgrade soon would this help much untill I can swing for a new alt. Thanks