advice on audio set-up

[Astrosfan]

I plan on this mod taking some time so i need to stagger it order to not drain my wallet.
My original plans:
kenwood dvd/nav probably the dnx6960
$200+- for front components
either a 8" bazooka tube or a custom 8" fiberglass enclosure
amp

I currently have a 250.2 RF amp, its old but works.
I really hate the base audio system but really need to get a clearbra installed so the dvd/nav is going to have to wait.

So, i was considering installing my amp and buying a set of components while using the factory HU for now until i get my finances back in order. Is this even worth it? I will probably get another amp eventually, but thats a long time from now.