Hmmm. No disrespect intended, but 200 users on 2 cpus sounds a little small to me.

It really depends on how much work will be done on the server. True, in an OLTP environment the transactions should be small. However, if there is alot of back-end computation involved, 2 CPUs will not be enough.

Your best bet would be to get a server that has the ability to scale to 4 or 6 processors. You could start with 2 processors and see if your application becomes CPU bound. You can justify to management that you want to add 1 cpu easier than you can justify a new server.