Believe actually gave me more trouble on the last level than Samurai Blue did. I'm not sure why, but it might be because I play SB on Hard enough that I had the beat patterns memorized(and they didn't throw too much new in to trick you on that one). Also, Believe is evil, the bar drops faster than the beats can refill it, and because of that I don't believe it's possible to finish the song with more than one miss. I know one is possible because I've done it, though even then you barely pass.
Anyway, I finished Countdown tonight, so all I've got left is the last song with the girls, and then hidden circle mode if I decide to give it another chance. I guess I'll probably be forced to try to play with the hidden circles if I want that last rank, and I do, because I'm still around 25 million points away and I don't think the last song alone is going to do it. It's not like my scores are really low either, I have at least half the songs S ranked on Hard, and I've got a couple S ranks with the girls as well. I could definitely go back and get better scores on a lot of the songs on the hardest level, but again I don't think it'll be enough.
The last song doesn't seem too bad actually, at least once I got over the shock that they actually added more beat markers to the last song in the game somehow. I can consistantly make it to the third section(actually the first two are quite easy), and after just a few tries I'm almost finishing the third section as well. I'm sure that last section is going to be the problem, since that's what messed me up on Hard so much.