NEED SOME HELP & ADVICE ON PITBULL! PLEASE HELP ME OUT HERE!?

hey i am wanting to get a pitbull puppy at the moment, perferably a red nose. i already have 2 springerspaniels (1 male and 1 female). i believe if you bring them up properly they can get along with other dogs but i need some advice here please i dont want the male springer and the pitbull to fight so would i need a female pit or what??. i also have plenty of chickens and ducks in the garden and was hoping to build the pit a doghouse so it could guard them as the fox is very alert and has killed afew ducks over the past few weeks. please could someone help me on this topic it is very urgent. ive tried foxtraps and to be honest have wanted a pitbull for a very long time now so please can someone help me.. people say they are agressive but its a myth, i have a 7yr old brother & i belive if brought up the right way the pit could get along with both the springers and the birds, please help me out here someone as i dont want to make ay wrong steps,,