First thing I would do is take one of the speakers from the back and hook it to your home stereo and see if it works. But, DONT leave it hooked up for long. see if you can get some sound, if so, its not the speakers.
But, if all of your speakers went out at the same time, id say the internal amp is shot.
If they work on your home stereo, then your head unit may be toast. I would recheck the wires first. Hope this helps