Hey
As I see it, the best option would be to buy a DSL router (with PPPoE). They are pretty cheap these days. In Norway they're starting at $100 and the you get a combined router/switch. The switch part let you connect more machines to the router. If you get a dsl router, you don't need to configure MiamiDx to use PPPoE. You configure most settings in your router (like PPPoE and DHCP) and then you configure MiamiDx with dynamic ip, gateway and netmask (via DHCP).
I've never configured MiamiDx to use PPPoE, but I configured MiamiDx to use PPTP (to connect up to a vpn network). It worked great. My dsl provider uses PPPoA (simillar to PPPoE), but I've got a dsl router which does everything a lot easier.
Have you read the MiamiDx.guide/NODE_TYPICAL_DSLPPPOE? Did you try to do this stuff? Didn't it work out? You should also read the FAQ at
www.nordicglobal.com/Amiga-DSL-FAQ.txtedit:
Genesis can be brought to support PPPoE using a thirdparthy device but only if you've got X-surf/X-surf2.
Good luck!
Regards
Tor