As you know about
Audacity[
^] - why not download the source and study it?
I don't think VS 2008 pro has anything you require, that C# 2010 express doesn't have, except C++/CLI - but that might come in handy.
I'd start with VS 2008 pro - at least you'll be able to leverage C++ at need; and take long look at audacity.
Best regards
Espen Harlinn