I used CruiseControl.NET as the continuous integration server for our Delphi builds, which blends perfectly with NAnt as the build scripting language.
Forgetting CC.NET, just using NAnt will provide most / everything you need, I think.
Combined with the optional NAnt-Contrib advanced features library, I implemented everything you mentioned, with the exception of Oracle integration. However, you can easily call command line elements from NAnt scripts or write your own NAnt tasks using any .NET language.
NAnt has tasks to integrate with Subversion, or you can simply invoke the svn command-line client.
I called BeyondCompare as a diff tool from my NAnt scripts, used NAnt to send custom HTML emails and run the Installshield assembly, and also obviously ran the Delphi compiler and commmand resource compiler.
NAnt is free and open source, worth checking out.
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