4 weeks is a bit young to leave the mother- 7-9 weeks is more standard. I'm surprised that the breeder is even letting you take the pup that young. Be certain that this is a reputable breeder- boxers can have hip problems, and the parents should be screened for them. Also, boxers are a high-energy, high-intelligence mastiff breed that can be quite territorial, and keeping a number of them in the same house may bring fights for dominance, especially multiple dogs of the same sex. The rescue organizations usually won't even place 2 dogs of the same sex together. Lots of boxers end up in rescue because their owners didn't realize what a high maintenance breed it is.
I like the names Max, Rex, Chief, etc. for a big regal male boxer. i used to have a female boxer x named Tess who carried herself like a queen, and a couple of my friends referred to her as The Contessa, lol.