getting a second dog...

The book Katz On Dogs by Jon Katz has a great section on getting a 2nd dog.  It was very helpful to me when I was considering getting a 2nd dog.

I'll check out that book

We have been considering getting a second dog for a while, and have looked into it a great deal.
 
From what we have found:
 
It is better to get a dog of the opposite sex of your resident dog.  There is more of a tendency of dogs of the same sex to have problems with each other.
 
I have gotten mixed responses on the size of the dog, compared with your current dog.  We have an APBT who really likes to play hard, so people have suggested we get a medium to large size dog that can keep up with him.  I have though, on the other hand, come across many people who live in harmony with both small and big dogs in their house.  I think you have to judge your dog, see how he plays with smaller dogs, consider whether or not you think he would hurt a smaller dog (obviously not intentionally).  Some dogs don't get along with certain types of dog.  You know your dog, and I think you will make an educated decision.
 
In terms of energy, you may want to get a dog that can keep up with your dog.  You don't want a senior dog that is going to be annoyed with your dogs always wanting to play.  But consider, do you want two high energy dogs in one house?  It may be a blessing in disguise, or could drive you crazy. 
These are all things to consider.
 
I am sure that someone living in a multidog household will be along shortly with some first hand advice.
Keep us posted on what you decide.
 
 
 

We would be getting a puppy if this happens...I am thinking of taking in a friend's rottie for an overnight as a test. Niko loves him anyway, I just want to see how a full day goes.

I disagree about having to have opposite sex dogs.  I've had dogs my entire life, usually two dogs at a time, and always had two males together without a problem.  Currently I have two male black labs and they're the best of friends.  Naturally within the dog world theres going to be the occasional alpha/beta squabble, but once the dogs realize that you, the master, are the alpha male, then you can keep them in line if they get out of hand.  Usually one will naturally be the leader of the other one and it may follow age, size, or just natural aggresiveness.   But I wouldn't hesitate getting two males.  The trick is to teach them early that you're the boss, and that you have complete control over them.  At an early age get them used to you holding them on their back, checking their toes, ears, mouth, privates.  Also teach them early that you can take their food away from them at any time you want.  That way you'll never have to worry about them fighting over a toy or bone, because you can simply step in and take it without fear of getting bit.  I can't vouche for two females together, but two males...no problem.  Enjoy...!!  

Try to match energy levels,  maybe get a dog a bit more lower key and perhaps smaller than your current dog. Not saying that's an absolute, just a suggestion, as your current dog may find this less intimidating.  I too have heard and read many times over that it's usually best to get opposite gender, but that may depend more on the 2 dog's personalities than gender itself. 
 
I used to think it would be impossible for me to have a 2nd female dog since my husky never seemed to care much for other female dogs. Then it occured to me that all the female dogs she ever met were hyper..... and she hates hyper dogs with boundless energy that dash up and get in her face.  She is a couch tater to the nth degree, so she is the polar opposite....perhaps if one day we should meet a personality twin for her it may not mattter...anyway that's just rambling. good luck with finding another furbaby.

If you were to get another dog, my vote would be for a female. Opposite sex of what you have.
I do have 2 dogs that do not play, but I do think that they enjoy a relationship in that they have each others company when we aren't home.  1 is male, 1 is female.  Never any problem. 
I have had 2 females that pretty much ignored each other.  I also had 2 females that would have killed each other, they started out very playful, it was great for about a year, then all "h e double toothpicks" broke out.  It is a gamble.
At one time I hired a trainer that told me that dogs should not play with other dogs, this was of course to try to help with the killer females.  She said that dogs do not have to have another dog to play with to be happy, which is one of the reasons I got the other dog also.  I am not sure I agree with everything this trainer said, however, you may want to just consider having playdates with other pups in the area.  You don't want to ruin a good thing you've got going.  
 
 
     

I have 3, two males and a female. Resident dog, is Dingo. We added Sammy who is extremely energetic. Sammy is 20lbs. and Dingo is 65lbs. They play, kinda. Then we added Tootsie, a pembroke welsh corgi and she and Sammy play non-stop. Dingo, is the old man of the two, so he usually just supervises.In regard to getting opposite sex, the two males are great, but if we added another female with Tootsie, there would definitely be some problems. Tootsie can be a real b****.