In case anyone else is geeking out over this as badly as I am, oracvalues.com lists antioxidant levels for a variety of foods in μ mol of Trolox Equivalents (TE)/100g, and indicates that cacao has 55,653 μ mol TE/100g, 40,200 μ mol TE/100g if Dutched (Wikipedia is listed as a source, which does make the accuracy open to question, but this can be checked; it also includes this statement:
The Linus Pauling Institute and European Food Safety Authority state that dietary anthocyanins and other flavonoids have little or no direct antioxidant food value following digestion. Unlike controlled test tube conditions, the fate of anthocyanins in vivo shows they are poorly conserved (less than 5%), with most of what is absorbed existing as chemically modified metabolites destined for rapid excretion. [Source: Wikipedia]).
A standard dark devil's food cake I make uses 50g cacao (27,827 μ mol antioxidants, using un-Dutched cacao). If no one is looking, I might eat an entire 1/8 (two embarrassingly generous slices) of the cake at one go (3478 μ mol, from the cake layers alone); if you're smaller than Andre the Giant, half that is a more typical, sane serving, since this is a pretty rich cake, what with flavoured whipped cream on it and all (1739 μ mol antioxidants).
Of the items listed, pecans are a fairly common thing to eat 100 g of in one go, and from that you'd get 17,940 μ mol TE/100g (about 10× what you'd get from that chocolate cake). Clearly, the thing to do is have a honking huge slice of cake, than assuage any nutritional concerns by eating a bunch of pecans (followed by a half-marathon, if one's figure is a concern).
Getting back to the OP, I've found that the key to getting a rich, full flavour from whatever chocolate I'm using is to bloom it in boiling water (I often tweak recipes just so I can do this, since my choices of cacao are not generally than fantastic where I am); this has given me good results even from the cheap, iffy crap I've occasionally picked up at ALDI.