Crowding is only one variable in a comprehensive orthodontic evaluation. Considering the fact that teeth are continuously moving throughout one's lifetime and unless a consistent retention schedule was followed (are retainers still being worn...do they still fit?) after the original braces were removed, it is possible that some significant changes may have occurred. Crowding is the most obvious noticeable change that patients can directly see. Problems such as crossbites, rotations of back teeth, jaw asymmetries, bite interferences, opening and closing deviations, and other jaw discrepencies are not so obvious, but can be significant issues requiring more extensive treatment. One can have perfectly straight teeth and still have a severe orthodontic problem.
The point of all this is that each patient should be presented with all the facts so that they can make an informed decision. Treatment options can then be presented once the patient is aware of the facts of their specific problems and can then select an appropriate option (after hearing the pros and cons to each option) that is best for them.
My advice is to see an orthodontic specialist and get a comprehensive evaluation. Select the best option for you (whatever you think it is). You can always elect to proceed with Invisalign to straighten your front teeth as long as you are aware of any limitations (if there are any) that may result from the option you choose.