Choosing the right JavaScript framework

I want to develop a web application that contains a lot of graphic elements (charts, menu bars, buttons...). The purpose of the application is to provide some tools to analyze charts. I use the js library 'Highcharts', and the web server side is written in python and I use the framework 'Tornado'. The client side will be witten using HTML5, CSS and JavaScript.

Here are some specifications about my app:

• The app must have an option to upload files with numeric data, in order to send them to the server, analyze them and make the charts.

• I need a fast communication with the server, for example: If I click on a graphic, I will need to send the information about that point to the server, and it has to reply me with the information about that point in the graphic.

• It also allows the user to select an interval, and the information of the interval selected will be sent to the server, and the server will reply with the information needed to refresh the graphic and only show the selected interval of the original graphic.

• I use the MVC2 pattern.

With these specifications, the doubt is: I'm not sure about which framework is the best option in order to satisfy the previous specifications. (easy graphic elements management, fast communication with the server, modular code, compatiple with all web browsers and screen sizes, etc ...)??

I'm grateful to those who help me solve my doubt . It's urgent.

PS: At the moment, I've only considered the following frameworks: Shencha EXTJS, Bootstrap.