Actually you do not need Miami DX unless you need a DHCP server. Miami has a built in DHCL client that works well, I am using it on my Amiga now with dhcp and it works fine.
Again DX is only if you would like to use Amiga as a true server as a client you can use Miami or Miami DX.
Thjere is only one thing that could prvent Miami not connecting and that is if the server conection (NTL) requires ppoe tunneling this is not supported by Miami and you must use Miami DX. I f you buy one of the cheap cable dsl routers available now and set it up for Static routing on the LAN side (not very complicated on most routers exept of course Microsoft routers

you can even use Genises or AMI/TCP, which by the way are faster than miami.