Hi,
Ok, SCSI to Ethernet adapters exist and can be found on ebay quite cheaply now.  They work with Apple Macs on the SCSI bus.
Most people have an SCSI interface on their Amiga and a 2nd hand SCSI to Ethernet adapter is much cheaper and easier to find than an Amiga Ethernet card. Just look on ebay.
I know there are no AmigaOS SANA drivers for SCSI to Ethernet adapters (abandoned project at 
http://theweeks.org/toms-stuff/ENET-SCSI.html)but will they work with MacOS under Shapeshiter, Emplant, Fusion to access a network from MacOS, or will they work on Linux/NetBSD?
I know that the Mac emulators can be told to use an scsi.device for what ever scsi adapter you have so surely MacOS would see these Ethernet adapters and use them as if they were on a Mac.  Also if I am correct that the drivers for them also exist for Linux/NetBSD m68k, then surely they will work on the Amiga!?
Bottom Line:  Has anyone tried an SCSI to Ethernet adapter on an Amiga Mac Emulator or UNIX???  If so what happened, and if not please try and and let me know what happens.  :-) 
-Beakster  ;-)