My 2006 had the NAV system. Would it benifit at all from better speakers and no amp upgrade?

Not sure what the radio in the NAV unit puts out.

I think maybe just silencing the Accord would be the best solution. Has anyone done this? I wonder how hard it is to remove the door panels?

I silenced my Tundra when I had it. Even though I replaced the HU and speakers, the biggest gain in sound was after I sound proofed it.

Check out: http://www.gwfweb.com/tundra/pages/sound.htm