I'm debating about the Teaching Company DVDs. Even on sale, it's a pretty big investment for something I'm not sure DS7 will like. Have you used them with your DS, LMom? Do they work well for kids like ours? Is it mostly a guy lecturing, or is it visually interesting?
DS6 got "The Joy of Mathematics" for his birthday. We've seen only a little bit of it so far, but DS was fascinated and so was I. But then the course is highly recommended for gt math kid and it's taught by Arthur Benjamin who is a very good lecturer (as you can remember

) I will have to write about it once we get a little bit farther in the series.
This is the only course I got from the Teaching Company so far. If it goes well, I may try others. I know nothing about the History of Math though. Any chance your library would carry it? Try asking on the Davidson list about math history books.