There's lots of good information on introducing cats. There is plenty on this site and I would recommend highly, reading and learning about introductions. Although there are never guarantees, if you do it slowly and follow the steps things will more than like be just fine. There are many knowledgeable people on this site and I'm sure you will hear from them too. I think it's wonderful you're thinking of getting another kitten and generally, it is easier for an adult cat to adapt to a kitten...not so much a threat. Also, your cat is still on the younger side so there's a great chance for them to be buddies. We got Lewis last December, he was 4 months old and my other two were 1 1/2 years old and they were very happy to have another wrestling buddy. We'll want to hear all about your new kitten if you decide to get one.