I'm not an audio noob, I'd say I'm simply a novice. I have some more advanced questions for the audiophiles. If any of this sounds completely wrong I'd be humbled if someone corrected me.

I'd like to wire up some components in the rear 6x8 slots of my FD, just the woofer however. I don't want a two way, and I don't want to use the tweeters.

I want to be able to specify the frequencies that are passed to those rear woofers through the head unit, is that possible? If so how would I go about it? (I generally want to filter out all the highs and be able to change the low pass frequencies on the fly depending on the music I want to listen to.)

In the front doors I'll use a shallow 6.5 inch component setup and a single 10 inch WS6 sub in the rear in a small sealed box. Head unit with be an AVIC F900BT and I'm considering just running the speakers off the head unit for the time being.

 

You have to use the preouts in order to change the frequencies on just the rear speakers. Some headunits don't have the lower frequencies pass through the "front" and "rear" preouts though, as those go through the "sub" preout.