What do you use to monitoring CMTS and the clients

Hello everybody,
I have question, What do you use to monitoring CMTS and the clients?
I use Nagios Version 2.9 build April 10, 2007

My question is:
What should I use better, faster with more option monitoring?
and one more qeusteion:
What are monitoring and what would you recommend to monitoring?

P.S execuse my english, thanks.
Thanks for all the ideas