I've got 15-20 heavy users on a LAN using Windows Server 2003 and XP as clients. I am using this as a Terminal Server. The students in my class often run multimedia-intensive content. What would be wiser - getting a Pentium with hyperthreading (3.06 with 800 fsb) or Load Balancing with another box the same as I already have (Athlon XP 2200)? Is it possible that these two actions will not give enough return to warrant the expense for my 15-20 users? Here's the present system: Athlon XP 2200, 2 GB Ram, 10/100 PCI NICs.
I can't really comment on whether it's worth it expense-wise, but if this current (powerful) configuration isn't doing it for you then I'd try adding another box. Processor power and memory are only among the possible bottlenecks for a Terminal Server, and also adding a second box gives you a fall-back position in case something happens to the single Terminal Server.
If you're using MetaFrame, you might also consider using content publishing to remove some of the load from the Terminal Servers and put it on the clients. MetaFrame XP FR3 also has some media-supporting capabilities that could come in handy.