Thanks for the feedback guys...
I've just plonked down the princely sum of US$1.60 (which includes shipping!) for a simple USB audio dongle.
If it works, then I'll be happy, if not, then I'll still be happy I tried, even if I'll be poorer by the cost of a cup of coffee! :-)
The lack of wireless USB networking is a bit of a pity. If it was possible, then I could keep my Amigas in a separate room, away from the PCs. But it looks like I'll have to sit them on the same desk and use a USB-Ethernet dongle to get me connected to my network router.
Cheers,
Mike.