SID 6581 & Speakjet Chip

I want create a circuit with a SID6581 and a Speakjet chip. Is it good enough to combine the audiooutputs from both chips ?

You mean by having each go thru a resistor (to keep each from impacting the other), and the junction on the other side going into an op amp or something? Yes, that should be doable. http://masteringelectronicsdesign.com/solving-the-summing-amplifier/

Are 200Ohm resistors good enough for the job ?

Maybe - what is the voltage swing of the 2 outputs, and do they have enough current output capability? current out = Vout/resistor value. So if they went +/-5v, with 200 ohm they'd need to be able to drive 25mA. If you're summing with an op-amp, I would go higher, keep the current required down.

If you do some googling on "audio summing circuit" you can find discussions like this: http://www.audiokarma.org/forums/showthread.php?t=71598 http://www.electronics-tutorials.ws/opamp/opamp_4.html

So it really comes down to how strong the two source drivers are.