Mounting Front Speakers
One recommendation is to use the original dash speaker location to mount two smaller speakers and if you need more bass output to put hidden larger bass drivers under the seat, behind the dash, or wherever else you can hide them. Look at this link about half wa down the first page for a couple of options to mount two 4" speakers in the dash opening.
http://www.forabodiesonly.com/mopar/showthread.php?t=129759&highlight=back+speaker
Then you could put an underseat 6" or 8" flat sub for bass reinforcement. It ends up sounding pretty good.
Food for thuoght........