To be honest, I am not a big fan of your style. I have developed a few hundred eccomerce sites. People come to a store to by stuff, they want to see products. Your header and most of your featured items need to show above the scroll. The right side link area can be much smaller giving you lots of room to display 2 featured items across the page. Also, if you want some seo gives us some text about why your site is special. If your a huge store and only going to use PPC then you don't need to worry about seo.