I am looking at upgrading just my head unit can this be done with keeping the subs with no issues?

I was planning on using a PAC ford adaptor, it is overkill for this setup but it will make my life easier and I can get it for a good price.

My plan is to run the front radio rca to the door subs with the pac harness, I do have a self powered MTX that I will run the sub out to for full control to my trunk sub. Use the head unit to power factory and or aftermarket speakers off the head unit for the time being.

feedback would be great, I am not putting amps and doing all that stuff so just comment on factory intragration with an aftermarket head unit...