Obviously looking through every possible seal for every make & model in existence in one list is impractical, since that is the way yours is set up. By entering the stock URL for the "top" category, I could find out that you have your products all in one category, Residential, with a Commercial category that is empty. I don't suppose there's much point in getting into a long discussion about ways to make the customer feel more in control of the experience... I would suggest that if you only want them to give you the precise model number at the start, that you make an explicit and prominent link near the search box directing them to the page where you tell them how to find their model number. I think I would be put off by a home page that would give me nothing until I entered the right code.
On another note, I see that you have had an "SEO" URL rewriter added to your site... but how are the URLs it makes really easier to understand than the stock Zen Cart ones? I see a bunch of gobbledygook in them (I know what it means, but most won't) which obscures the name and model. This will not help SEO. If you enter a URL with less than the full gobbledygook, like [your domain]/fisher-paykel-c120p-fridge, you will get page not found; how is that useful? Your info pages have no meaningful words in the URL beyond page.html?id=3. If you think you need to rewrite the URLs, get a good rewriter that will give clean URLs, like CEON URI Mapping in Free Addons.