Bandwidth Monitoring, maybe Packet Shaping eventually

I'm getting some DSL services installed and I need some recommendations or even a pointer or two to a method of long-term bandwidth monitoring while keeping latency to a minimum. The DSL for our customers will be coming into our location on an ATM. I'm still working out the details with static or dynamic IPs, but either way, I need to monitor bandwidth for each incoming DSL connection and although placing a 'slink' server between the incoming ATM and our network would be frowned upon for latency concerns, a 'slink' server that can monitor this bandwidth and create logs to be processed monthly from a location outside of the initial subnet would be highly revered. Specifically, any software that can monitor bandwidth and create logs (CSV or, even better, SQL) would do the trick: I can tailor the equipment and connections to suit the software; I just have to locate the proggie to do this.