Just get chickens! or chicks. I have done a lot of research, and thought for sure I would like this breed and not that... only to be surprised. Some you do like better. In the next months you will be able to walk into nearly any farm store and buy chicks of the breeds you mentioned. This, more than likely, will not be the last time you buy chicks, if you take to this hobby. So you don't really have to get it perfectly the first time.
Just get started! 6-8 is a nice flock. For a first time operator, I strongly recommend just pullets or chicks that will be hens. Grow them up, get some experience, and then you can add other aspects of the hobby such as hatching eggs, having roosters, meat birds..ect. You don't have to do it all the first year.
Mrs K