It's the site that gets the forum members, your site is not of a kind I can see dragging people in. People come here initially to discuss the articles on the site and get advice about their own equipment.
Because your site is a business (where as Anandtech relies on advertising for its income (or so I understand)) you are never going to get the numbers. Provide people with another service on your site, such as reviews, tips or a column and more people will be inclined to want to discuss something.