Only you can answer that question, really.
Things to consider are:
First off, can you afford to take care of a dog in addition to the cats? Are you prepared for the different costs involved with owning a dog? They eat more (depending) they need more personal time and attention, they have WAY more demands and they develop different health issues than cats do.
If you can afford the dog and provide for it properly, (food, attention, healthcare, etc.) then explore all the options and needs, weigh the pros vs. the cons and make your decision.
I’m sure you know all this, and are most likely a responsible pet owner, but I just like to cover all the bases when it comes to people questioning about whether to take on another pet….so please, don’t take this as criticism, but rather as just good advice.
Just remember, the thing about owning ANY animal or animals is that they depend SOLELY on YOU for their needs. Love, care, attention, etc. it all lands on YOU. If you can not love the animal and consider it to be a member of the family and not just an animal or novelty, then you don’t need it, nor deserve it.
Animals give unconditional love – they love you no matter what you do. If you can not do the same for the animal, then no is the answer.
Dogs and cats are different, think it through, learn about the breed you are interested in getting, read up, talk to other people, go online and join forums related to the breed or just dogs in general, and make sure you’ve got what it takes.
Do your homework and you’ll know whether it’s the right move for you. And please consider adopting or getting a rescue before buying from a pet store. The last thing we need to do is keep promoting pet stores who deal with puppy mills. Adopt, don’t shop.
Best of luck!
Oh – and another thing – Make sure that if you do this, you won’t be putting any stress on your relationship with your wife. You stated that she thinks you’re crazy for wanting a dog—but does she really mean that or is she just making a silly statement? Something to consider. Some people won’t voice their true feelings about things until you pin them down…...so that’s the other thing I would do. Make certain that it isn’t going to create any waves between the two of you.