Electrical Wiring Issue, Help greatly appreciated.

Hello yall, I have a 06 Nissan Altima, I installed a new HU today (kenwood dpx702bh) and I'm all finished up. One issue maybe two.... When I start the car and my headunit is not on (because I did not hook up the ground wire yet) my amplifiers turn on just fine. But.. when I hook up my ground wire behind the screw that holds the headunit in place, my headunit works just fine but my amps turn off and have no power. So if that was confusing..... Headunit on, amps go off. Headunit off(from lack of ground wire connected) amps come on as normal. Any help would be great. Thanks again