C# / .NET SIP Soft Phone with custom features

Need a soundboard softphone written using any decent open source library you would like, for example [login to view URL] I would prefer it if you would use a phone that has a G.729 library available, which liblinphone does, so that bandwidth can be saved. If you have experience with existing SIP and RTP libraries that is a plus. The target platform is Windows. The soft phone would have an array of buttons which can start and stop recordings to playback to the far end just like a common soundboard used on the radio or podcasts. This could be used for either special effects or for pre-recorded presentations. Additionally, there should be the capability to mix in a looping comfort noise track wav file and also the phone user's microphone, so your programming capability of manipulating real time audio is a must. As far as the soundboard UI is concerned, the buttons labels should be definable by the user, and the wav files behind them can be swapped out for a different folder of files using a drop down menu.... i.e. multiple voices with the same labels and key layout. When editing the soundboard labels, the buttons should have drag and drop to re-position, delete, and modify. Additionally, the UI should have stay-on-top mode and global hotkey keystrokes definable so the messages can be started and stopped with the keyboard and the mouse. The UI should also have an interface to record from the user's microphone or import existing wav files from a local file folder. The finished product should support WebDAV storage for central administration. This includes the phone's configuration files and of course the wav files. As far as softphone features, the typical DTMF dialpad and functions available in the underlying SIP/RTP libraries. Additionally audio control so the user does not have to tweak Windows sound settings. We can discuss specifics more. Thank you for bidding on this project and good luck!