Sql-server – IIS Express, SQL Express as production server

According to the SQL Server 2005 Express edition overview:

there are no limits to the number of databases that can be attached to the server.

So, the limit is how much performance you can utilise of the server. Consider that as the express edition will only use one CPU core, if you have a quad core processor it can not use more than 25%.

If you later on find that you need to utilise more of the server's performance, you can quite easily upgrade to a different version of SQL Server.

The other editions of SQL server get you things like the SQL Agent so you can schedule database maintenance and other jobs.

As long as your database can fit withing the limits of the Express edition you'll be just fine.

SQL server likes lots of RAM. The more the better. As the SQL Server can't load data into cache that'll put additional load on the disks. You should look at the Web Edition or Workstation edition of SQL Server. Those editions have higher limits than the Express edition, but cost less than Standard Edition.

If you do start with the Express edition, you can always upgrade later to the Standard Edition after you purchase the license.