I believe both the 16-ch ADAT Sonorus STUDI/O which is now obsolete and can be had used or the 16-ch ADAT Frontier Designs offer PCI cards that work in both the MAC and PC. No AES though. Alesis makes a dual ADAT I/O optical to 4-pairs of AES interface, the AI4.

Hi MacBlack, check out latest RME cards ..
MacMod

RME are the clear winners in this category. Their Hammerfall cards put basically zero load on the CPU and have extremely low latency (down to 64 samples if your machine can handle it). I have used them for a couple of years and they are solid as a rock.

MisterBlue.