Hello,
I agree with mruffruff. You should not get a little chihuahua at six weeks old because you have a boxer puppy also. The boxer will deffinitely be rough to the little chihuahua. I have a chihuahua, "Chica". I got her at 12 weeks old and she only weighed 2 pounds. She was very small. You have to be very careful not to step on her. And also they need lots of human attention. You have to let them sleep with you in bed because they like the warmth under the covers. And they like to be next to their owner all the time. I had weewee pads and a ramp so the pup could get down off the bed and pee on the weewee pad and come back to bed. They are very smart and easy to train. They are very attached to their owner. She follows me everywhere in the house. I had to get up in the middle of the night when I first got her to feed her because they have to be fed 3 times a day as puppies. Now she is 14 months old and she is fed 2 times a day. She doesn't like me to leave her when I have to go to work or do my grocery shopping. Chihuahuas have anxiety seperation from their owners. But she knows the routine, and she probably naps when I am gone. I take her places with me also. She loves to ride in the car, or go for walks, or go to the park. So re-think getting another pup until you have your boxer completely trained and you can trust your boxer with a little pup. Okay, that is my opinion.