Normally, I'd say save your money, as a 166 and a good GPA should be as good as gold just about anywhere. However, since you're shooting for the extreme top of the heap, go for it. An extra couple of points really does seem to make a difference. Also, I think you really had a good reason to be mentally out of sorts when you took the test. If I had a nickel every time I heard "I was practicing in the 170's, but I really scored so much lower," I'd be a zillionaire. However, your circumstances really were extreme; good luck!