The only way that amp will ever make 1500W is if it gets hit by lightning!!!

NEVER look at peak power specs - they are a waste of time and are a marketing figure.

You can do one of two things with this amplifier for it to run a whole system.

1. you can run just the front components from two channels, and the sub from the rear channels (bridge them). If your components are 4 ohms, then they will get 65W each. If they are two ohm, they will get 125W each. The sub must present a 4 ohm load, and you will get 250W to it.

2. You can wire your front and rear right speakers in parallel. Do the same for the lefts. They both must be 4 ohm speakers. Then wire them to the front channels of the amp. Each speaker will get 65W. Then use the sub, bridged, to the rear channels. This will cause you to lose any fading capability between front and rear speakers.

I would highly suggest you run setup number 1. Run the rear speakers from your headunit. The first arrangement will cause the amp to run cooler (it's already going to double as a bbq) and will be easier on your charging system.

That amp is really only a 500W amp, but should be enough power to create a nice system.