Introduce them at the park a few times and see if they get along well. Do that and keep them around each other for a while. Once you think they will be a good match. Bring the dog to your house just for visits, since your dog is dominant, he might have a problem with a new dog all the sudden living on his property. So make sure they get along at your house too. If they do, then you should be ok.
If you get another male, your dog might not like another male on your property. So if you want to get a male, try to get one that's submissive, just to avoid a dominance problem.
If you get a female, make sure to get her spayed first, and get your dog neutered if he isn't already. If he is but the female isn't spayed, the humping will be a real problem, especially when she's in heat. So make sure they both get spayed and neutered.
Good luck!!!