Fourth kitty now or later?

Hi everyone, I'm new to this forum and would like opinions. We have a six yr. old cat-Phantom, a four yr. old cat-Quincy and a new kitten who we got a couple weeks ago-Boscoe. Phantom is tolerating Boscoe pretty well. Quincy won't run and hide when Boscoe is around but he decided he didn't want to sit on my lap (as he usually would) the other night when we rented a movie. Phantom was on my lap and my husband had Boscoe on his lap on a different piece of furniture but Quincy still didn't want to be even that close to Boscoe. Boscoe wants to play a lot more than Phantom and Quincy do and I think he's driving them nuts from that standpoint. We'd like to end up with four cats at some point. Phantom and Quincy are neutered males and Boscoe will be when the time is right. There is a little girl kitty available and we were wondering about getting her now-she's about the same age as Boscoe. I wondered if the two of them would play and give Phantom and Quincy some peace. But I don't know if that would be too much for Phantom and Quincy. If I waited a couple months and then got a new kitten, I'd be doing it to Phantom and Quincy again after things had completely settled down. I wonder if it would be better to get the second kitten now and just get this ajjustment period all over with in one fell swoop. So, fourth cat now or later? Any ideas?

I can't really say one way or another.

There's a chance everything can go great, but also the chance it will cause more turmoil.

The likely hood of the 2 young cats playing together is very good, but I don't think they would leave the older 2 alone all together.

If you've seen a significat change in your older cats behavoirs, you might want to hold off for a while on getting yet another cat. It can take months for things to be set in place and for cats emotions and territory instincts to be marked as normal.
Some cats change their personality perminetly, when presented with another pet to live with.
Asim is definetly one of those. His personality changes a little bit with ever perminate or foster cat/dog I have ever brought in. Sometimes for good, but often for bad (at least in the beginning.)

If your older cats seem almost uneffected by the presence of the new cat other then the "pfftt, leave me alone yougin." You might be able to pull off bringing yet another into the house.

I have had pretty good luck doing it both ways. As stated before, if they didn't get really bent out of shape, then I think it would be better to bring one home now.

Better now than later. The kitten probably misses its littermates, and would love to have a playmate. Let the two kittens play together, and introduce the older ones to the babies gradually.