then you will probably not find an all inclusive does what you need app. You will probably have to use 2-6 and merge them into a single interface/reporting tool.
MRTG will graph usage of many things, such as network activity, CPU/Memory usage, NTOP will monitor network stuff in realtime, Nagios is good for making sure servers are up and functioning correctly (i.e. offering services they should). Can use WMI stuff to pull Windows workstations stuff, etc.