Hey Peter. Like going from Windows 98 to Windows XP, you have to buy the new version. HOWEVER...you would first need to decide if going to the new version is worth it. Like going from windows 98 to windows ME...it's not worth it. I even know tons of people that wouldn't pay to go from Windows 98 to Windows XP. It's all personal preference.

For Collector's Assistant Plus, there are some new features, but essentially, it's the same. So if the new features aren't that important to you, then pass on it. You can see the different features and differences in the two versions online at the same link I gave you (Carlisle Development).