Alex,

I would make the category page Toy cars with the separate product links: Blue toy cars, Red toy cars, Racer cars, etc. By linking one higher category page to a lower product page you are establishing your own page ranking "Score" that is read by the search engines as higher or lower in authority.

Your meta descriptions will further reinforce this higher archery by having the category pages describe most of the terms used in the lower level pages. Then be very specific on the separate product pages.

Now if someone searches for toy cars your category page is a higher result offering an entire selection of toy cars. But if your customer wants to type a longer search term "Blue racer toy cars" they will be directed to your specific product page.

I think you may have already done that, and just not relized you have.

An example would be Binding #1 set up as yourdomaine.com and the second binding set up as www.yourdomaine.com . Check the SEOMOZ "Site explorer". First do a report on yourdomaine.com noteing the results, now try it on www.yourdomaine.com notice the differance in the results. and your right about the answer. The sub domaine does retain some of its DA.

I'm not sure if it is the correct thing to do, but in GWT, I have manually chosen to have Google use the higher ranking DA name as its default.

Just my thoughts.