Upgrading 2008 Standard Edition to SQL Server 2008 R2 Enterprise Edition

Hi All,

We need upgrade our SQL Server 2008 Standard Edition to SQL Server 2008 R2 Enterprise Edition, i have gone through couple of links as below.

http://msdn.microsoft.com/en-us/library/ms144267(v=sql.100).aspx

Wanted to know how do we upgrade from 2008 Standard Edition to SQL Server 2008 R2 Enterprise Edition, becuase here we have upgrade the Edition and also version.

Below link says we can upgrade from SQL Server 2008 Standard Edition to SQL Server 2008 R2 Enterprise Edition

http://msdn.microsoft.com/en-us/library/ms143393(v=sql.100).aspx


so my question is Do we have to upgrade SQL Server 2008 Standard Edition to SQL Server 2008 R2 Standard Edition Edition and then Upgrade the Edition to R2 Enterprise Edition

or 

else we can directly Upgrade from SQL Server 2008 Standard Edition to SQL Server 2008 R2 Enterprise Edition.

please guide me and also let me know with Pre and post Upgrade Checklist