Incidentally, I was checking out the Genius Intelligence before I purchased GMS. Although they are quite different things, I think they both have some merit. GMS of course needs no description- it seems like one of the best investments you can make- and Genius Intelligence I think might have some good information, although I am somewhat skeptical of Genius Intelligence with the whole brain waves thing and listening to audio to affect your subconscious. But in my opinion, they are hugely different. GMS is about memorization, Gen Intel is about your IQ and "raw brain power". It seems to me that GMS would help in these areas as well, although Genius Intel is geared specifically towards those areas.
I would suggest however, that you choose one and focus on it (and in my opinion, it seems GMS is more valuable). GMS seems like a substantial commitment from what I've experienced so far (I'm on lesson 4!), and you wouldn't want to be tied down among two important commitments.
That said, if Genius Intelligence is just a few e-Books with exercises, I suppose it wouldn't be bad to have them, and it would be possible to read them when you had time outside of GMS. On that note, it is quite a generous offer from LaGrange, and if I were you, I would definitely accept the ebooks. (LaGrange, if it wouldn't be too much trouble for you, and you wouldn't mind sending me a copy as well, that would be really cool, because I think there might be some benefits to the Genius Intelligence. I can you send you my email if you wouldn't mind sending me a copy)