Make sure that the prospective parents of your puppy are health tested for heart, hip and thyriod problems, and make sure that the breeder shows their dogs in Conformation to ensure that your boxer baby will look like a boxer when he or she is grown. Visit the breeders home prior to picking up your puppy to ensure that they are cared for in a proper manner. Ask pointed questions about temperament issues like aggression, shyness or fearfulness, separation anxiety, etc. Make sure that the breeder does their part to keep our shelters from becoming overfull by asking if they will take the dog back at any time should you no longer be able to care for it. Expect to spay or neuter your puppy if interested in a pet quality puppy, or expect to show an health test your puppy when it becomes an adult if interested in a breed quality puppy.
Last but not least, have you considered rescue? Lighthouse Boxer Rescue has many adoptable dogs coming through their program on a fairly regular basis. The advantages of adopting an older dog are to numerous to list, but include: no potty training hastle, the dogs are up to date on vaccinations, spayed or neutered, cheaper than buying a puppy, and most come with some obedience training.
Good luck in finding your next family member. Remember, this is a decision that should not be rushed and can last throughout the next 10-14 years of your life!
If you're in Ohio, I'd recommend VanSan's Boxers. They're right over the border to PA and will probably even meet you. They are pure Boxer lovers and have really taken time and their life to continue the right lines. Their website is www.vansansboxers.com. Tell them Darren sent you! I drove 9 hours to pick our 5 month old from them and every single day I'm thankful for it. He's the perfect pup with regards to temperament, conformation, and just plain personality.
On that note, vansan's actually takes the time to run their dogs down to the university and has tests done every year. Their male, "Thunder" is a beauty! They even went as far as to meet me a few hours from their house and they brough the parents just for me to meet them! I thought that was great.
I do know of White Pines Boxers (Linda Gasper). I don't, however, know of KO Boxers and I'm pretty sure that they don't show, which makes me wonder if they do all of the appropriate health testing.
While I do believe that Linda has the best intention of our breed at heart, I always advise people (when dealing with ANY breeder) to request hard copies of the parents health testing. If the breeder ever had anything to hide, it would be pretty difficult for them to do so when dealing with hard copy proof of testing.
Honestly, I'd steer clear of Dead Broke Kennels (the link posted above). I usually don't bash other breeders on public forums (at least, I don't mention names), but I sincerely question this breeders motivations. I don't feel that they have the best interest of the breed at heart because their primary motivator seems to be money (or at least, the mention of stud prices, and "puppies for sale" right off the bat on their home page gives me this impression). They don't show, so they can't even be sure that the boxers they're producing look and act like boxers (and many of them don't compare to our standard) and there is no mention of health testing. In a breed that is plagued with many lethal (or debilitating) health conditions, I really can't stress the importance of health testing enough. No mention of take back, co-ownership or spay/neuter clauses. . . which all make me wonder if they're contributing to our shelter/rescue problems.
Worst of all, they've bred Kea FIVE times. I would likely never consider breeding a bitch more than three times (or, at least, she'd have to be a pretty darned good outstanding representative of the breed and an outstanding producer for me to consider it). Five is in line with the number of times that most puppy millers breed their bitches and I would NEVER even consider it.
Again, I'm sorry to be so blunt, but to know that kennels like this exist (let alone so close to me) really bothers me.
Interlude Boxers is in West Bend Indiana. Google it and you will find a nice website with lots of information. She thoroughly health tests and has been in the business way over 35 years and knows her dogs. I don't know if she has pups now, or pups planned, but sometimes she can refer you to people who have litters by her dog. I really would recommend someone who is buying a puppy supports a breeder who is health testing this breed. I had no problems with any health issues with my dogs until my last three (in a row) with heart problems. I am adamant about getting my dogs from someone who TRULY loves this breed and wants to minimize those issues.