You are going to be owned by a Boxer. They are wonderful dogs and they require a big commitment. Sounds like you are doing your research. Taking out in the morning, noon and evenings free with the pup will be nice. Coming home at noon for an hour would work for the older dog, but you will need to have an arrangement fixed up to suit the puppy on being left for the 4 hours inbetween. I would recommend getting an Ex-pen, or exercise pen for the little one versus a crate. Make it smaller to start with, but leaving enough room for a potty area so he/she doesn't have to sleep in it and has room to play when you're gone. Use a pee-pee pad and make sure to use a mess clean-up such as Nature's Miracle to clean up and accidents in the house so they don't repeat on a spot. Little ones won't be able to wait the 4 hours inbetween outings the ability to hold will increase with age and probably by 6 months they will be able to go with your schedule.
As for the cat. I would think you will have no problem with that since you have a puppy joining your household. You might need to be vigilant about monitoring the play between puppy and cat, telling them to "mellow out" if/when it becomes too wild. I have a friend who has 6 German Shepherds who let a cat live in their midst due to her leadership. You can do this if you want to.
I would recommend a book called "Mother Knows Best" by Carole Benjamin. She has some excellent recommendations on all aspects of dogs. Another good book is "If Bones Would Rain From The Sky" by Suzanne Clothier. This is a little "heavier" of a book and I would not recommend it as a starter book for a new puppy owner, but rather for further reading once you have read and studied Carole's book. Also enroll in a good obedience course with your puppy when he/she is 4 -5 months old. You might want to take it more than once. Please try to find one that is not a PetSmart one. I train dogs and recently witnessed one of their classes and it wasn't worth 2 cents in my opinion. Find a Praise Based trainer and sign up for the classes they offer.
Welcome to world of Boxers....Like Nano said, prepare to be owned and it's not said in a bad way either...They will steal your heart forever...We just brought home a second one for a companion to our senior..Boxers are best in two's...
Research is a great thing and anyone that takes the time is a better owner for it...
I work from 7am to 3pm, and my babies do ok during the day. I come home around 11 to let them out for potty breaks. Gunnar does fine with this arrangement, he can hold it. Our 13 week old, Ginger, is gated in our entry. I put out food, water, a blankie, and a potty pad. She seems to be doing fine with this.
Also, we have 2 cats, a 7 year old female, and 6 year old male. Both cats were here before the dogs. Everyone gets along fine, although the dogs sometime like to chase the cats. That is the main reason we chose a puppy over an older boxer. My cats are definitely the alphas around here!!
Nano is right (usually is :wink: ). The cat sould be fine. If you can, enlist the help of a neighbor to let puppy out. Also, the longer a pup stays with its litter mates, the better. Getting a 12-week pup as apposed to an 8-week pup would be better.