I use the digital out of my iMac to a Benchmark DAC1 and I am quite happy. I didn't want to use an adapter and didn't have to, Monster makes a cable that has mini-optical in one and and regular optical in the other (I think I paid about 45 dollars online).
USB is probably better, but I didn't want to replace my DAC for that.
USB is probably better, but I didn't want to replace my DAC for that.