Here's my feeling on that: When you say you are targeting "all major categories of product" I (rightly or wrongly) think of an Amazon affiliate-type site. When I think of someone launching an Amazon affiliate-type site and trying to market it, I think the many tens of thousands of other, similar site owners who have underestimated the budget and/or the time they need to do market it correctly. In those cases, 99% of their products remain forever invisible to searchers.
I have to tell you, the fact that your site is about finished and you're just now thinking about marketing isn't giving me the warm fuzzies. The marketing of each product-- individually chosen to be on your site because it fits a need of your target audience and within your marketing--would best have been dealt with prior to the development of your site. If the sell-everything amazon affiliate had thought that way, they may have gotten a handle on how much total time they would be investing in their marketing, as well as how and to whom they'd be marketing them to.
But since you're just getting around to it, for each product, I'd be asking myself, "why this product", "who needs" this product" "when do they need this product", "what is the buyer doing that requires this product" "how difficult will it be to get this product to show up in the search results?", "How long will it take to get this product to show up in the search results?" ,"How profitable is this product", "What's my marketing budget? "When do I need to see an ROI?" and then I'd start tossing products from my site for which I couldn't those questions right off the bat, so that I was at least starting with a core bunch of products I know something about.
If you're not that kind of site, please excuse my rant.