I am currently using Sonar 2.2 but, I'm looking at upgrading to Professional. My question is, when you do an upgrade, to get the upgrade price, can you get the boxed version or does it have to be a download?

There is no physical media available at this time. All versions whether boxed* or not, upgrade or full retail are downloads. Cakewalk has indicated they will be providing physical media, burned on demand, at some time in the future.
 
 
*the boxed version contains a card with a product code for the download, a printed user guide and keyboard shortcut card.

Ahhh, very good. Thanks!!