There are so many dependencies for this, I just don't know where to begin.

How is the design of the database? Are the columns properly indexed? What kid of queries are each user preforming? How much data is being returned per resultset? The list is huge.

Why would you want to use an Express version in a Production environment? How do you plan to maintain the databases? Maintaining a database is so much more important that the number of users trying to access the database. Without maintenance, there will soon be no database.

I would almost say, that the database will not be there long. Without proper maintenance, the queries will begin to take longer and longer everyday.

Andrew SQLDBA