BattleOfBennington:
None of these products are going to convert your clay into black gold, but they could benefit your plants health against bad organisms.
As for your clay, before I moved my old lot used to have the worst clay EVER. When it was dry it was as hard as concrete, so hard that you couldn't work it with a shovel. Over 3 years I tried many things, and last summer I actually was able to grow and produce healthy plants in it.
If you want to be able to grow something in your clay lot this summer, google: Lasagna gardening. I had a lot of luck with this technique. If you don't want to spend the time feeding your soil and improving it over time, look into raised beds.
With lasagna gardening you will be feeding your soil and improving its quality. Then in late summer, early fall, right after you're done harvesting, plant a cover crop. Cover crops protect your soil from erosion, suck up nutrients so they don't get washed away, and break up your clay. I did a mix of Winter Rye and Hairy Vetch. These two cover crops survive the winter and restart growing in the spring. In early May I chopped the 4ft worth of cover crops using an electric hedger, and let the roots rot in the soil. I then planted my crops and mulched with the "hay" created by the winter rye and vetch.
I would recommend against tilling, I did it for two years and watched my clay get progressively worse. Check out Steve Groff's no-till website:
http://www.cedarmeadowfarm.com/