Radio harness powering an N7 and an AMP

I'm building a car tablet with the N7 but have one question about power. My current plan is to plug the tablet (via an OTG cable) into a cigarette USB and solder the power from the radio harness to that and store it all in the console. Does that radio harness have enough power to also splice a small amp as well? Or will I need to run the amp power down to my fuse box?

Thanks!

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