I have been looking into Ember.js, and it looks really great, but one thing that concerns me, and that I can't get my mind around it, is if I start using it on an already running project.

Will I eventually have to move everything client side, and make my application a single page application at some point?

let me clarify...

So far the best way to communicate between client and server using Ember is REST. and that looks great, but what I don't like is having all the templates loaded for the first time. and moving all the logic in my server to the client (or am I getting all of this wrong?), cause it looks like my server side will become a logic-less REST API.

Also, I'm using Yii Framework which has some JavaScript (Ajax enabled) components like grids. how can I have ember interact with all of this on navigation without having to rewrite a bunch of stuff already working on my application?

I'm on the login page (or state), and then after login in, I have to display a grid, that is just easy with Yii, and a full page load, but If I am using Ember, how can I have my grid display as it normally would? do I have to pre-load a handlebar template for the grid, and also the JavaScript that controls it?