This sounds like a job for SevOne, which has turned out to be the premiere networking monitoring software that is currently available. SevOne will give you very accurate utilization information, including Cisco Netflow analysis tools. Their appliance model is very appealing, it scales from 10,000 to over 1 Million monitoring elements without effort. Everything is Web based, the entire interface runs in a browser, no need to install cumbersome software packages. They employ state of the art custom hardware to acheive amazing performance. Basically, you can run reports at a monents notice and they are created from scratch, not from canned reports. They also don’t roll up data, which is great if you want to analyze historic information. In essence, you can go back today to a year ago and look at what happened in your network as if it would happen right now.
They are also reasonably priced, and they offer a hot standby failover solution, so if anything were to happen to your primary appliance, the failover would take over and it has all the data of the primary, which is just plain amazing.
I strongly suggest you check them out, www.sevone.com, they’d be happy to schedule a remote presentation with you and will ship you a demonstration unit if you are interested in that.