At this point, I don't think it matters what sex you get. Your male would just love to have a playmate. I find that some cats in play will seem to be serious when they attack, but it really is play. Perhaps you can arrange with the vet to be able to return the kitten if you find your resident cat becomes too rough
. 14+ kitties has a real good website for introducing kitties, hopefully she will come back and post it
OMG, you should see Japer and Sweet Pea play, the hissing that goes on (well really Sweet Pea does the hissing at Jasper
, until he backs off, then she goes in for the attack
). Hissing is not necessarily aggression, it can also be fear, or, a request to be left alone.