Looking just at the hardware and support costs, the upgrade I am considering is a no brainer. But before we can make a final decision on the upgrade, I have to go around to the independent software vendors and find out what piece of this upgrade action they will get. HP e3000 software vendors sometimes have many more than seven tiers. It is a chaotic mess that takes, in my opinion, an inordinate amount of time to manage. One of the nice things about Windows NT is that you do not really have to play that game.
Software is licensed per system and often per client access.
I have always preferred the per-seat licensing, since you can easily explain and justify the cost. If you have an application that uses SQL Server, you need to buy enough client licenses to support the users. It is easier to explain that to your boss than to try to explain why it costs more for the software because it is running on a PA-RISC 8200 rather than a PA RISC 7150 processor. Exchange 5.5 Enterprise Edition uses a different database technology that can support larger mail databases as compared to the standard Exchange product. There are also more connectors included so that the Enterprise can connect to more different e-mail platforms at no additional cost.