deactivate to move to new machine

You don't need to deactivate it on your old machine. Your license allows you to have it on several of your own machines, provided you only use one at a time.
However, when you attempt to activate Sonar on the second machine, you will get the message that Sonar is already registered, and you cannot register it again.
No worries. Log into your account at the Sonar Store.
Your activation code will be listed there, and you just enter it in the appropriate box on the new machine. The second copy of Sonar will acknowledge the code, and you are good to go.

Ah, well that was easy enough.  Thanks for the help!