Go with the battery and charger. I run that setup at home and it works fine. Obviously you can't run high power music for EXTENDED periods of time. But then again, I think you'd be having more problems with your neighbours if you were intending to pump that much energy out in a sessions. I run a JL Audio 500/1 and a 300/4 off a 570A CC battery with two 6A 12V chargers which was pretty cheap to set up at the time.
Basically this gives your ~ 144W continous power. Given that the RMS values are 1/root(2) x PEAK output of the amps (a situation which will rarely be achieved, and if so for only a short time) the power actually used by the amp is somewhat less than the stated value. Not to mention the overstated power output given by most amp companies these days - with JL maybe being an exception to that, but that's another topic.
Anyway the setup works a treat. Never had any power issues. Remember you can always charge the battery while not listening to music - or if you're finding you're running out of juice, add another battery and or charger.
I have seen (few and far between) some of those specialist 12V setups for use at car comps here is Oz. But the $$$ was quite excessive. In any case stick with the battery setup as it will act in a much similar way to a capacitor (in terms of supplying current in those ultra low impedance moments . You can always add chargers, transformers later.
Hope this helps,