I thought I answered this a few days ago, but I guess not.
As mentioned, the easy way to determine how much current you SHOULD have available is to go with the devices max draw spec. If you have two devices capable of pulling a max of 10 amps, then you need to have a circuit capable of providing that 10 amps. The 1/3rd and 1/8th power ratings are the more realistic power consumption specs of that device. If I am not mistaken, a 1/3rd rating would be about the equivalent of the power amp just on the verge of clipping. The 1/8th power rating is akin to the device being on and running at what would essentially be idle or nominal. The likelihood of actually running the speaker to a point where it will pull the max rated consumption is highly unlikely. While that may be the case, best practices and standards say that you should have a circuit that is capable of handling the full max rated consumption of all devices on that circuit. With most modern commercial speakers available at your big box stores or online, the typical number of speakers you can fit on one circuit is 3-4. Most powered speakers set around a 5.5 amp max draw. With a real, full 20 amp circuit, this means you should have no problem dealing with 3 speakers going full tilt boogie, adding a fourth can be done, but is caveat emptor. If you know you are just providing light background music, then you can get away with perhaps 5 speakers on a circuit if power distribution is that light. Again, caveat emptor though.
For me, I tend to run anything sub related on as many circuits as possible. If I can do 1 per circuit, I will. If not, then no more than two regardless of the current ratings. For mains and monitors, I run no more than 4 speakers per circuit. With my typical setup running 2 subs, 2 mains, 8 monitors, the band, and associated gear ( mixer, stage box et all ), I can get away with a minimum of 4 x 20 amp circuits. 1 for subs, 1 for the mains, mixer, and the stage, and then 2 circuits for monitors. Ideally, I would prefer a total of 6 circuits.
With your genie, you are limited to about 1,800 watts of actual consumption. Realistically you would want to run less than that. It is essentially a 15 amp rated unit. The rough conversion of amps to watts is to take the amps and multiply it by 120. So a 6.3 amp devise would pull roughly 756 watts. As you can see, by the time you have two speakers with that rating on the circuit, you don't have much available wattage left, assuming all get out. Again you can probably get away with running three speakers, but, caveat emptor.
