Yes there is an all in one solution
I have just fitted a Parrot MKi9200 to my 04 plate Jazz S
You can play all your music through the speakers, and the Parrot has a built in amplifier and equaliser.
You can make and recieve calls that come through the speakers.
And it also charges the Iphone.
Bought mine from Amazon think it was £150, and its way better than the fm transmiter things.
Jamey