i need advice on aftermarket audio equipment!

I have some questions about my jbl audio system in regards to upgrades.

I am considering upgrading the front speakers with the polk sr6500? any idea if these will fit?

Where does the jl cleansweep go in the circuit? Is it between the factory stereo and jbl amp or is it between the jbl amp and aftermarket amp?

How big of a sub do I need? Right now I have 2 10" JBL's to use....would one suffice, would two be too much? And will I need a separate volume control for the subs?

Changing out the fronts and adding the cleansweep, amp, and sub seems like a simple way to get great sound, no?

Looking for a system to make melane: !