MusicLaw has a good point to run an Ammeter on it for actual power usage. the 60 Watts is rated max, so it probably doesn't hit that draw and probably operates significantly less.
Here's why this isn't as simple as your solution:
5a / 12v = 60 watts
for planning (battery capacity deteriorates, so conservative estimates will last longer over time and use):
6 hours play time
360 watt hours / equals 30 amp hours
include the 85% inverter inefficiency = 55.5 amp hours
for deep cycle batteries, damage occurs at greater than 50% discharge:
111 amp hours for 6 hours of Helix play time.
The reason this makes me nuts is, all the other gear (6 other devices for 6 hours) only needs 23 amp hours and doesn't require inversion.
Using the same calculations above minus inversion: I need 46 amp hours (round to 50) for all other devices, and 111 amp hours for Helix because of the insanity of Inverting DC to AC, to power a device that wants DC in the first place.
Thanks for this reccomendation jbuhajla - I never really considered a gas generator, and these are appreciably quiet.
The 1000w @$400 would make the rig simpler to design and operate, and would cost about the same as a deep-cell battery battery solution.
But it's not as "green" or techie cool, and is not silent.