We looked at this where I work..... (Score 1)

First I'll assume you're in a windows / intel environment and it's beyond your power to change that. So be it. Where I work we did a little testing and benchmarking and talked to a citrix / windows-ts sysadmin or two. The general rule of thumb we came up with is: 1 high-end processor + 1 gig of RAM = 10 happy users. Please note: that's CORPORATE users... running resource hogs like outlook and having 15+ windows open all the time. Also, like another comment stated... ferret out ALL your costs when you do your analysis. Also, I did some college lab management a while back and noticed that all money is not created equal... money for equipment may be easier to get than money for staff, depending on the financial and political environment at your institution. Don't forget, this thin client stuff is a bandwidth hog. No problem for a well-designed switched lan, if you have that. Figure 30 to 100 KB/s AVERAGE per user for average office apps. MUCH more for multimedia. Citrix will tell you as little as 7KB/s. Don't believe them.