Hello.
  Don't know about NetBSD/amiga, but I'm using 3c574 on NetBSD/macppc
(1.6.2):

ep1 at pcmcia1 function 0: 3Com 3c574-TX 10/100Mbps Ethernet
ep1: address 00:60:08:b6:60:4d, 64KB word-wide FIFO, 1:1 Rx:Tx split
ukphy0 at ep1 phy 0: Generic IEEE 802.3u media interface
ukphy0: 78Q2120 10/100 media interface (OUI 0x00039c, model 0x0014), rev. 3
ukphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto

Just works.

Greets
Radek