PsiWin 2.3.3 (I think) will work with OS9, so maybe you could try installing that in Classic, and using a serial to USB connection when connecting with the PsiLink cable. I'm actually contemplating doing the same thing with my old 3a.
I just bought a 3mx on eBay, and plan to use the irda capabilities to keep my address book up to date. Whether that's possible is another matter!