Similarly, if you're going for an ADSL connection, any ADSL Modem/Ethernet Router should do the job. The router takes care of your Internet connection so all you need on the Amiga is a TCP/IP stack and a driver for your Ethernet card.
I bought a generic router from Dabs (part of their value range) when I got ADSL and it's been great.
The model I bought has been discontinued but
eBuyer do one for just over 30UKP, the quick find number is 48449.
HTH
Robert