If your current data isn’t in great shape, you might consider re-entry as an option. This doesn’t have to be a lot of work for you, however. Your Rock instance will come with a branded registration page that will allow your attendees to input their own data. This has the additional benefit of allowing them to easily setup a login for future personalization and self-service features.
Note that if you use an external giving service that integrates into Rock, they can often import past giving information into your new Rock instance.