JJ: As I said before, the card is of course only 802.11b, and my router only supported g/n. Got a new router that supports everything and gigabit wired. Netgear N600 wireless dual band gigabit router (WNDR3700). Nice feature about it is it supports 4 different SSIDs. So I can have my always running 2.4 and 5 GHz SSIDs as secured as I can make them, and open an isolated guest SSID as the router refers to it for the Amiga. A useful feature, as also my Nintendo DS only supports WEP encryption, and I also rarely go only with it.
Gil: The router acts as a firewall, but I don't think that's what you mean. As for the filters, I think I can set a fixed IP per MAC without too much hassle. Your other suggestions are great, but I don't know how to implement them in the first place, and they'd be impossible for the various game consoles that have internet access. Possibly for the Amiga, too. It may be able to do the finger match, but I don't know about the rsync daemon.