We are beginning to build out a webapp which will probably see a lot of traffic. We dont have a lot of money, so we want to reduce hardware cost. More or less, I think that mean
Spring MVC and Stripes would be on my short list.
Both are light and easy and gives you more flexibility of the web application.
You might also considering looking at AJAX functionality; which parts of the pages could be simplified/smaller due to the usage of AJAX.