I have written several scripts for use as Cacti data sources to collect detailed statistics from various DSL routers.
Zyxel Routers
The zyxel_dsl_router.pl script supports monitoring of sync rates, noise margins and error counts for Zyxel routers. It is known to work with with the P660R-61C router but may work with others as well.
Billion Routers
The billion_dsl_router.pl script supports monitoring of sync rates, noise margins and error counts for Billion routers. It is known to work with with the B5200S router but may work with others as well.