I used the dd-wrt method successfully some years ago. But it was very difficult to configure - hopefully the tools have improved since then!
More recently I've been using Apple routers for this. Set a Time Capsule to "extend a wireless network" and everything plugged into the Ethernet ports is now online. I think you could do the same with a basic single-port Airport Express and hanging a standard wired Ethernet switch/hub off it for the Amigas to plug into. Since I also have Macs this option made sense for me (and paid for itself in number of headaches avoided!
)
