I do not consider the Rascher mouthpiece to be too dark. It all depends on what your ideal sound is. In answer to your questions, yes, it is a responsive mouthpiece. The altissimo range is unlimited, as long as you take the proper time to get used to the more closed facing. I was not able to play as high on my Rascher right after switching from a Caravan, but in time I got it back. You must know that as you go towards a more closed-off facing, volume will suffer to some degree. It is in the nature of open-chambered mouthpieces to be this way. Also, what sax do you own? That can be a factor in choosing a mouthpiece as well.