I wouldn't just pick one guy and have to order from him. Look at all of the ones mentioned and see who has what you want and who has the best prices.
I order from several different people and have had mostly good results from most of them. A lot of my fish are from Ken becuase he hooks me up with some really nice stuff when he gets new spawns, new fish in, or gets back from collecting. Plus his shipping is by far the cheapest for me. If you are in NC he can ship to you really cheaply compared to others.
With that said Jeff has a larger stock list and if Ken doesn't have what you want I would check there next.
If you want larger fish such as pairs or adults I would check with Ira as he always seems to have more 5"+ pairs then anyone and all of his customers seem very happy with there fish.
Like I said before, search around for the best deal. Find what you want make sure the person has positive reviews and you will be happy with your order.