If you put them in with a white male you will know for sure if they are carring two pied genes or one , if the mating produces all pieds then they have 2 pied genes if they only have one pied gene they can produce blues, white and pieds.
If you put them in with a blue split white you can get pieds,whites and blues .
If you put them in with a pied male with one pied gene they can produce white,pied and blues.
It depends on what you like really. I personally would put a white peacock with them because I would be wanting to breed for pied peafowl, and breeding white to pied gets you some white peachicks and some pied peachicks which is a pretty good deal. When you breed pied to pied you get three different things and thus have a bit less of a chance to get pieds if that is what you are going for. It should be easier for you to find a white peacock also. For me at least it was hard to find a nearby pied peacock when I first got into pied peafowl.