Are you using WPA or WEP?
BTW WEP is so insecure its not even funny. i can crack WEP encryption in like 3 mins.
I think I got WPA2 running, Im in no need of more security I could even use WEP or nothing (most people can aircrack WEP super fast), I have no one close to my house who can access my Wifi also it's managed by my FreeBSD pfSense machine and has no access to the local network via wifi so it's no problem at all, the only machine that uses wifi is my A1200 everything else are via cable (htpc cable+homeplug).
So even if someone would use a laptop from a car outside my house I feel safe enough to not worry whith my neatly managed pfSense machine and without access tot he LAN what are they going to do, hack my A1200 the few times I go online with it or download porn

.
Edit: Also if unknown devices would access the Wifi it would trigger an alert and I would look into it.
Also im quite sure I could configure pfSense to only accept connections from the Amiga and nothing else if I felt it was needed.
(pfSense is the best thing ive invested hardware in for networking in a long time, im glad i dug into it after we moved and I got my new fiber 1000Mb/s connection).