dilectio implies, in addition to love, a choice made beforehand... and therefore dilection is not in the concupiscible power, but only in the will, and only in the rational nature.
When I say, "I love donuts," the love I mean is not one of choice. I don't elect to love donuts, I just love 'em ("from necessity and not from free-will," as the Good Doctor would say). This kind of love, of amor, is an act of my sensitive appetite; I apprehend donuts as pleasurable. (And, incidentally, I think the imprecision of the word "love" is preferable to going about saying things like, "I apprehend donuts as pleasurable.")
Of course, I also might ("might"?) dilect a particular donut, in an act of the will urged by a passion of the body. But that represents a free choice on my part (on the assumption that I can conceive of some good in doing something other than choosing the donut).
Now, the dilection St. Thomas has in mind as the principal act of charity isn't just any kind of dilection. "Charity is the friendship of man for God," so to act out of charity is to act out of friendship, and friendship is wishing the good to someone with whom we have "some sort of communication."
And here I'll wrap up by explaining why turning on the television to see what's on ESPN is a good idea. According to Aristotle, "goodwill is ... the beginning of friendship." Since we are called to have charity toward everyone, we are called to have friendship toward everyone, and every friendship has to start somewhere.
With goodwill, for example. And, as St. Thomas points out,
goodwill sometimes arises suddenly, as happens to us if we look on at a boxing-match, and we wish one of the boxers to win.