For those of you who do not want to get too deep into changing the car. Have you considered taking advantage of the modern trend of portable bluetooth speakers that link up to your Smartphone. Not a replacement but meant as a leftfield suggestion in case it helps.
They are battery powered and give up to 10 hours use
They are removable from the car (hotel room for trips etc?)
They can bluetooth or cable to an iPod or smartphone making the controls handy
They can be in a footwell or on the backshelf depending on other load
They avoid changes to the base car.
Quality example
http://www.amazon.co.uk/Bose-SoundLink-B...uetooth+speaker Or perhaps one for Aldermog
http://www.amazon.co.uk/Tailgater-Blueto...uetooth+speaker Not all of them can achieve a good sound but it does make for a light/simple solution that brings other benefits so I raise it to see if it helps. The sound quality of them is improving all the time as this becomes a mainstream product.
Works in car/hotel/home
Bluetooth means you can control it from your phone which is close to you and in line of sight if you have a clip mount.
Just trying to give an option. I would still do what Firewood has done. I was looking for the same for my Aero S2. Same issue with volume and quality but not everyone wants this messing with the fun of a jaunt.
