I have recently had a new sound system and have rear speakers in the rear side panels.

They are likely to rattle and make the sound awful but there is a acoustic material called 'DYNAMAT' that sticks onto the back of the panel and deadens all the vibration and unwanted noise. It has the added bonus of improving the speaker performance also. It will set you back about £10-£15 for a roll to do both sides. I can recommend it as mine sounds great now.

I also fitted an alpine amp (used for 1 output) and a sub in the back. I chose a small box for the sub so I don't loose much space. I was worried It would spoil the sound a little , but again I can recommend it as it actually sounds good.

The amp is quite small and fits in the side locker out of the way of kids feet and wet dogs! There is more than enough space around it to vent the heat. (I still have to find a suitable grille for the sub to keep the dogs wet nose off it but in the mean time it is still removable).

In the front I fitted a couple of good quality 4" component speakers (Audiobahn) to replace the Toyota ones (they came to £60+vat because they were a bit difficult to size correctly so the choice was limited) and a couple of tweeters on the dash.

A good quality head unit will have a band pass filter to let you switch off the lower frequency bass to the ordinary speakers and let it all go to the sub instead. That stops any unwanted distortion when the volume us up.

I used a Pioneer with MP3 Playback. The plastic blank was made for a Celica (Halfords part so a bit of a rip off) but can be trimmed to fit and looks tidy.

The only snag I have now is how to stop the rear view mirror from shaking in time with the music...!!

The bottom line is that you can fit rear speakers successfully with the help of under £20 of dynamat and it does improve the sound dramatically having the extra speakers.