I've heard of people running those sundown amps at 0.5 Ohms... but
You have no electrical upgrades and a big huge draw might drop your voltage low enough that it would be dangerous for the amp @ 0.5 ohm. I would say don't run it at 0.5 ohms until you do the big 3 upgrade with 1/0, run 1/0 to the amp, have a nice solid main battery, and your alternator (if stock) is not worn out and is keeping the voltage up.