NRG and MRTG use the same kind of setup. It's actually pretty easy to setup once you take the time to find out how (there are some scripts included to get the basics). They both work by using snmp GET (not traps). So if you have a dsl router that supports snmp you can use either. Once you know how to setup monitoring for 1 router it's just a matter of copy 'n paste and changing the ip to add the rest.

Edit: You will want to monitor the DSL routers, not the switches/hubs. The switches/hubs will give you an idea of the LAN usage not the up/down stream bandwith of your dsl connection.