a) Link either doesn't exist on main page or isn't immediately apparent enough.
b) Consider this page - http://www.boostclassifieds.com.au. Today is the first time I've seen it - visually it looks horrible and potentially untrustworthy. If I may say so, your site looks freakin' incredible. But on their site, the first thing my eyes land on is a gigantic list of categories. It takes me FIVE seconds to find the link to "turbos and superchargers" and one click later I'm where I want to be, looking at what I want to buy. Which I guarantee I'm doing right now - in fact I've spotted a couple of GT280RS that look pretty good to me.
I had to navigate through so much shit to find the search page and look for turbos on your site that I didn't actually want to bother.
I'm having trouble with the balancing act. I definitely need to improve the searchability of the site. At the same time if I put everything front and center it'll become pretty apparent that we don't have many listings yet. Will that just turn people away? I'm not sure yet, I don't have the data to say.
I'll think more on this.
But so will a site with no listings at all, as yours appears.
The first thing you should do is split the site: A big "For sellers" / "For buyers" right at the start, then each group can navigate their own section. Perhaps a third button to talk about what you do, what's special about your site.
The site has so much style it's unusable. And what's with the B/W photos? They look horrible. Even on the detail page I have to mouse over it to get color.
People go a site like yours to get stuff done, not to chill out and look around.
P.S. I apologize if I sound too harsh, I'm not always good at giving criticism online.