Maybe i'm a dummy, but I cant find the amplifier for the speakers.

I have an '08 a4 with the audi symphony (not the bose system). I was under the impression it had an amp for the speakers, does anyone know where it is?

On a side note, I'm going to be putting in a new headunit with a built in amplifier, anyone know if the stock amplifier will cause problems?

 

It won't cause problems as long as you know what you're getting into. In cars I've dealt with in the past, you had to get the right wiring harness for how you wanted to wire it. You either use the preamp outputs on the head unit and wire it into the factory (or a new, standalone amp), or you get a wiring harness that bypasses the factory amp and use the amplified outputs on the head unit.

Either way is acceptable, just don't run the amplified outs into the factory amp. I'm new to my Audi, so I don't know much about the Audi factory amps, so I can't tell you whether you should bypass it or use it--someone else will have to get into that.