Quote Originally Posted by JimmyHAD View Post

If you don't have him fixed soon marking territory will become ingrained and you will always have that as a problem. All of the normal dominant male cat behavior that makes it tough for the owner and the neighbors will disappear and you will have a better pet than you have now. Go for it, don't wait.
It's done... I had him neutered this morning. He is now in that stoned post-operation state. I hope he snaps back soon.

Thanks for the input, everybody! I feel much better now...