Aftermarket Headunit with Aftermarket Amp
 

So I recently bought a new aftermarket class D microamp to replace the factory amp for the door speakers. I connected the low-level outputs from the factory Headunit. Everything works well but now I want to install an aftermarket HU. I just wanted to ask if I need to connect the low level outputs going to the amp from the RCA outputs of the aftermarket instead of the included harness. I'm thinking the output from the Metra harness is high-level meant to go directly to speakers without an amp.

Delete this thread, found out that my Pioneer GM-D1004 amp has an automatic signal-sensing feature. Doesn't matter if it's high or low-level inputs

You'd better use the low level inputs between the hu and amp for sound quality reasons