The issuse will be bringing him into their territory. If he does not submit to your dog, then there can be a problem. Introducing them on neutral ground will tell you if they initially get along. It won't tell you how your dog will react to an interloper in his home. When I was looking for a third dog, I had my dogs both meet them at a neutral place, walked them together, etc. Everything was fine with each dog they met, until we walked them home. Then Cody said no. He was not letting them in his house with him. Even though they were female, and "should" have been okay, it wasn't. Neither of them were submissive and growled back at him. That did not fly with him at all, so we kept looking. If your dog growls at the new one and the new one submits to him, it will be okay, as long as the new one doesn't just bide his time and continue to push it. If he eventually does bow up back at your dog, there will be a fight and the loser is expected by the winner to leave, unless they submit during the fight. That is dog logic, unfortunately. "You did not submit. You kept fighting and I beat you. Now you leave and don't come back." That is what I am dealing with now, with my pyr and my wolfhound. The wolfhound was torn up, had to go in for surgery to repair his chest and the pyr is determined to get to him to finish the job. They cannot even be where the pyr can see him through a door, without the pyr attacking the door, trying to get to him. Good luck.
Kathy