Hi all, I have just started to hack the arduino sid library:
Sid Arduino is a library developed by Christoph Haberer & Mario Patino. Sid Arduino emulate a C/64 SID chip very closely, allowing you to get a '80 amplifier for free on your arduino.
My version is able to output SID voice2 on Pin 10, so you have two output: pin9 voice 1,3 pin10 voice 2
Consider to connect an external amplifier for better performance. If you like it give it a try and let me know. Enhancement requests/questions are welcome (file it on github)!