looking for diagram programs

I am looking for a good car stereo diagram program (a la visio or autocad)  that i can use to create  a schematic of any projects that i work on to give to my customers. it should be able to show how the radio connects to the amplifiers (if more than one and if there are any crossovers) and how the speakers are laid out (in what doors, if they are components) and also show power wiring distribution. anyone know of any programs that do this?  many thanks

i'm hoping to find a program that will have premade icons for each item, that way i can just connect items.  any one else have any ideas?