Given the dearth of source material at 192, I would just use the optical out on the mini or macbook. Eventually, you'll be able to use the hdmi for it.
The optical on the macs will do 24/96. As to the 16 channel part, unless you're doing more than 2 channel out, that doesn't really help you .
An alternative would be a firewire sound card. There are several that should fit your needs without requiring a mac pro.
Then it depends on your taste . I don't think the ESW9 is hands down better htan the HD600s well amplified, but I preferred them. I do think the ESW10 straight out of my ipod was better than any senn I've tried out of my m3.