I hate to be a huge ego-buster here, but the look you're seeing on women's faces is probably NOT joy or amazement, it's probably more like fear & trepidation.
I have encountered two men whose penises measured over 9" in my life, and both experiences were filled with pain, choking, bleeding, and much discomfort.
Now that I'm older, I might be able to 'take it' better, since I'm more able to express myself during sex and more openly tell a partner that he's causing me pain or discomfort.
Be proud of what you've been given, but for heaven's sake, be careful with that thing...it's dangerous!