A great but undocumented feature in SONAR’s Loop Explorer View is the ability to preview multiple files at the same time.
Use the Ctrl and Shift keys to select multiple files.
Then when you press Play in the Loop Explorer all of the files will playback in sync. If a file is already playing, using the Ctrl and Shift keys will add the files to what is already playing, allowing you to build your MultiTrack loop in real-time.
After finding the loops you want to use you can drag-and-drop the multiple file selection from the Loop Explorer view into the track view and import all of the files at once. Please see the Getting Started With MultiTracks in SONAR tutorial for more information.