should the "head" unit /cd player - power front or rear?

[CDK 10+ year member]

That looks fine ...
If you can get one cheap, the TS-W12PRS is by far the best subwoofer Pioneer has ever produced ...

http://www.pioneeraus.com.au/car_entertainment/subwoofers/tsw12prs/index.html

I don't see it on Pioneer Australia's site, but my next choice would be the TS-W1241C ...

http://www.pioneerelectronics.ca/pna/product/detail/0,,32171715_32252631_35788755,00.html

The TS-W305C is a better choice as well, IMO ...

how about amp?

JBL better than pioneer amp?

JBL GTO755.6

http://www.jbl.com/car/products/product_detail.aspx?prod=GTO755.6&ser=GTS&cat=AMP

or

Pioneer GM-6100F

http://www.pioneerelectronics.com/pna/product/detail/0,,2076_183982242_152786492_tab=B,00.html?compName=PNA_ProductDetailComponent

This is to power the speakers only (not subs)

JBL amp i could get it cheaper than the Pioneer 6100F.

 

[CDK 10+ year member]

I'd take the JBL if you can get it cheaper ...
That'll run your whole system ...

is it better?

hm?