Transposing Virtual Instrument Clips
You can transpose a Virtual Instrument Clip by clicking on the Sound Details tab on the bottom of the window.  Click on the drop down entitled Adjust To Project Key and choose Transpose By.

Then either type in or select the number of half steps that you'd like to transpose the clip by.  

Virtual Instrument clips can be transposed without audio degradation because each time they are played the synthesizer recreates the sound from the MIDI data.