You can load the 64-bit version of the ARIA Player in Sonar with the following steps:

  1. In Sonar, go to Options > Global > VST Plug-ins.
  2. Click the Add button to add the folder path for ARIA 64-bit VST.
  3. Once you have added the correct path, check the "Re-scan Existing" and "Re-scan Failed" boxes. 
  4. Click the Scan button.
  5. Save the settings, then close and relaunch Sonar 64-bit.

You should now be able to insert the 64-bit version of ARIA in a SONAR project.