PRTG Network Monitor XL5 - license + 2 Years Maintenance - unlimited sensors, up to 5 core server installations of one

RTG Network Monitor runs on a machine within your network, collecting various statistics from the machines, software, and devices, which you designate. (It can also autodiscover them, helping you map out your network.) It also retains the data, so you can see historical performance, helping you react to changes. PRTG comes with an easy-to-use web interface with point-and-click configuration. You can easily share data from it with non-technical colleagues and customers, including via live graphs and custom reports. This will let you plan for network expansion PRTG can collect data for almost anything of interest on your network. It supports multiple protocols for collecting this data.