One thing you
could do is use a background for the content #content .pageContent and change it out when there isn't a sidebar.
Code:
.Sidebar #content .pageContent { background: url('background1.png'); }
.NoSidebar #content .pageContente { background: url('background2.png'); }
Still, isn't exactly pretty, and there are times when it can be problematic but it's less of a pain then using an equalHeight plugin which doesn't work with responsive design all that much (I had it included in the framework, but it was either building our own take and test hundreds of use cases, or remove it. I chose the later
).