Another question about car audio wiring for rear components

[YarisSedan]

So my rear deck has 6x9 subs. I have some tweeters that came from my old components that used to be in the front. They have a built in crossover. I have the subs wired directly to the amp. Is it possible to use the existing factory wiring to power the tweeters seperately? So they are powered by the deck while the other speakers are powered by the amp. Or is this not a good idea.

Another option is i have another 4 channel amp. My front speakers are bi ampable so i can use the amp to power the rear tweeters while the other amp powers the rear subs. And then use the front channel to power the 6.5 subs in the door while the other amp is powering the front tweeters.

My only questions is where do i get the other rca signal? There is a output on the deck for rear channel thats not being used right now. But for the front channel for the front subs i would have a input. Unless there is some way to splice the front channel from the other amp to the second amp.

Sorry for all the questions this is my first time getting into doing any wiring on car audio myself but its a fun learning experience.