Commercial T1 bandwidth monitoring

I have a simple yet very important question. Here is the background: Our network has multiple T1 lines from different vendors that are dedicated to it's own portion of the network. We do everything from Cisco VPN connections for remote users, Shoretel VoIP systems internally and over the VPN to remote users. We run our own Exchange, and Web servers and multiple file  and database servers.

One of our T1's is dedicated to the VPN and the VoIP and Mail data that is transferred over it to our remote users. I am experiencing some really weird connection issues to our mail server and shoretel systems over the VPN.

This has been going on a while and we are not sure what is causing this. The VPN remote users worked better when we had the VPN sharing our other T1 line with other systems. We get the VPN it's own dedicated T1 to handle the new VoIP traffic and the VPN connections have become more unstable.?@#^$%@ It is very weird.

I would like to know if anyone knows of any software or hardware that can monitor our T1's bandwidth usage. We have looked at a few packet shapers that can do this but the company is not willing to spend any more money on or systems just yet, at least not till they prove reliable as they have just revamped all our systems to top of the line equipment a few months ago. So I am in need of a inexpensive way of monitoring out T1 lines traffic in real time. Either a hardware or software solution as long as it is not too expensive.

Thanks,

Nugs