I think I have finally decided to run the Polk db571's in the front and rear. Should I just get an aftermarket HU or should I get an amp to power it? Amp would give me the option to tune it to my liking with the Xover.

 

you'll get the most out of them with a quality amplifier.

 

Absolutely get an amplifier. I put two sets of those Polks in my brother's Escape with the stock Nav HU and a little Alpine 4x50 4channel and it sounds miles better than a HU powering speakers.

 

Ok, I know I am repeating myself but how do I hook up the amp to my HU? I know I don't just wire the speakers to the amp. I need to get the signal from my HU to the Amp for the speakers. Does that make sense?

 

Rca Cables from Headunit to amp then speaker wires from amp to speakers

 

Right but i have stock HU. I don't think there are any RCA jacks.