2002 Buick Rendezvous strange No start

Hello,
My wifes 2002 Buick Rendezvous will not crank. Good Battery, Good Starter.
Its acting like an electrical problem. Suspecting a bad connection or ECU?
Turn key on, hear weird noise out of speakers. Starter will click but not crank. Dash lights tend to flicker. Engaged crank relay manually and motor turns very very slow and drains battery.

Any help appreciated.