We're finally going to be able to attach a real SID chip to our Macs!

Check the HardSID Mac-blog here:
http://osx.hardsid.com/Some details:
(Click topic header for full list)
The HardSID 4U is the most powerful SID synthesizer since the legendary C64!
Two CPUs and main memory
USB connection (compatible with both 2.0 & 1.1)
Isochronous USB endpoint for low-latency audio
VSTi interface with 8000Hz update rate on all SID registers (free)
Wave-in VSTi pin for routing 8000Hz signals to any registers
(example: playing other VSTi's sound on the volume register)
Full automation of all VSTi parameters
Superior sound quality (..it is a HardSID!)
Support for up to four SID chips (6581/8580/6582 in any combination)
Updateable firmware over USB
Cycle-accurate playback of your favorite SID tunes
Digitized sound + high-speed playback with low CPU utilization
Seamless playback of .sid tunes while you work on your PC by providing a huge playback buffer for non-VSTi applications