I had Titan neutered at 18 months. He didn't calm down one bit! He is still a psycho! What I have found interesting is that now that I got him nuetered, he is constantly trying to hump Harley! What gives? Actually, I think it is a dominance thing due to age. He has been more brave during their toy battles. It's like he is testing her to see if she will say "uncle".
Another odd side effect. He has always slept on my bed, but would usually not be touching me, unless his head or paw flopped my way. But since the day I brought him home from the nueter, he lays smashed up against me! I think he was traumatized by being left there and he's afraid if he isn't touching me I will sneak away or something. And I wouldn't mind, but it breaks my back!