third party performance monitor

I have an NT server with 85 PCs, 100 users, and 15 printers. Its the only server, so it is the domain controller, print server, file server, etc. I want to run HelpDesk software managed from a server and also an InOut Board. Administration wants to add Exchange server and also run multimedia training software for our staff.

Of course, all this stuff can’t run on one server. But I’m being pressed to prove that with benchmarks or performance logs that say the server has a full workload managing users, security, file access, and printers. The problem I have with the Performance Monitors in NT/2k is they don’t seem to match what my instincts tell me. Does anyone know of any third party software that can help me out? I can’t allow my domaincontroller to be loaded down with any more tasks.