Hi Marc,
Affiliate banners and no original content is fine, but I think a little re-organization may be needed.
First, I had a similar site, (it is gone now) for a variety of products and one thing I did was to make sure all the banners were the same size (468 x 60) and the layout was something like this:
- Title of the Product
- Brief 2 sentence description
- Display the banner
Blank Line
- Title of next product
- etc....
Secondly, I would use the side navigation bar instead of the top, for my taste the site is too wide like that. I think with the products offered it is easier to read from a list i.e. top to bottom vs. from left to right.
You offer alot and I think making the visitor's ability to easily navigate is a "must" other wise they will get lost and never return. This could be part of the reason why no sales. If a visitor can't find what they are looking for right away, they will go some else and look.