This is what I would like to do:

Mount 6 x 9's behinds the seats, in the plastic/ w amp

Is this possible? and how should mount the speakers and where to mount the amp?

Reason: I don’t want a sub, but still what a bit more sound


( I have a 04)

 

I don't think that a 6 x 9 will fit in that plastic. If you take the panel off you will see that there wouldn't really be room for the magnet. I did however quite easily fit some 4" round speakers in there. I mounted my amp where the spare tire goes. No need for it when your sub removed your jack

 

Another owner on this board recently told me that he has 6x9s in the back of his S, but I have not actually seen any pictures and it is the first I've heard of it being done successfully. As far as I know, there are several owners who have managed to fit 4", 4x6" and even 5.25" speakers back there. FWIW, your money may be better spent on high end components (for the doors), an amp, and sound deadening as a start for improving your system's bass response (if this hasn't been done already).

Listed in no particular order...
S2KPUDDYDAD's 4" Polk setup
synergytone's 4" Polk setup listed for trade ages ago
Huntsmcgee's 4x6 Kicker install
kenta's 5.25" Polk setup
Search specifically for the phrase "Where can I mount my amp?" on this page

 

Thanks guys for the info. I was thinking of making a spacer that would mount to the plastic so the speaker would be raised and there for making enough room for the magnet.