Evaluating bandwidth capacity - what reports do you use?

I am in a situation where we need to look at each of our remote sites and evaluate the bandwidth capacity and use patterns, then answer the question of whether we need to increase bandwidth at any of the sites. There are some sites where we seem to have periodic congestion issues. We have NPM, and NTA installed and I think we may need reports from each to help us make our decisions. The question I have for the community is. what reports would /have you used to evaluate the bandwidth at remote sites?

Thank you for any suggestions.