Change the width of the main content div

This may be a silly question, but isn’t there a way to make the body wider than the 730px the content/sidebar width appears to be restricted to in the layout settings? I’m going to be putting many slideshows in an image-centric website and don’t want them to be quite that small, especially since I’d like to add a left sidebar. It would be great if I could make the page and slideshows responsive so it was smaller on tablet and mobile, but I’m guessing the theme doesn’t allow for that (I’m using http://easingslider.com/). So perhaps better to just leave the width at a safe 730px? (e.g. see http://stackoverflow.com/questions/3375706/ipad-browser-width-height-standard)

I don’t see any reference to 730px, or the styling that is making the main content div so narriw in the CSS. If I do something like this, it does adjust make the div wider, but I also want it centered and that part isn’t working…plus I’d like it to be responsive which I know I’m breaking. There has to be a better way–help!

<div id=”content” role=”main” style=”width:1000px; margin-left:auto; margin-right:auto”>