When I told a woman who keeps chickens I wanted a mixed flock, she told me they wouldn't get along, my sister told me as long as they grew up together I shouldn't have a problem. So I have 12 birds of 5 varieties. If you read these threads they will tell you to mix similar sized birds. Don't throw little guys in, they will be scared of larger hens and most likely chased by them. These threads will tell you to separate by wire only at first so they can see but not touch each other, and I was told by the feed store girl to put new chickens in at night so they wake up together, instead of throwing them right in.
I would definitely get a few more because if the new and old don't blend, the new will have each other to run around with. Hope this helps!!
I forgot to say that at this point get whatever breed you want, because the transition will not be super smooth even if you get more Marans.