Stealth sound system install on a Duster

Anyone played with adding nicer sound to their Duster/Demon? I found two places in the back passenger bench headrest area for speakers (looks like 6x9), and I also have the stock AM radio + dash speaker. It's awful.

All I want is nice, not perfect. Perfect is for living rooms and mine is full of parts and stuff. Mostly the sound of the road is all I want, but sometimes it's good to crank some music.

I'm thinking - and all of this will be used to save $ - basic and hidden deck/receiver that also plays mp3s off a thumb drive, basic amp, modest subwoofer box in the back, 6x9s in the back headrest area, and a pair of 4x6s tucked under the dash.

The existing radio controls (and the push buttons turned into momentary switches for next/back for mp3s/cds) could be rewired out and used to control the hidden deck while looking old and uninviting to thieves.