Jack- This is one of my four. Its classic and just fits.
Simon- just doesn't fit, can't really give a reason. It just doesn't.
Rowan- This doesnt fit. Its Irish and none of your others are, and just sticks out with the others.
Avery- one of my four. Can't really think of a reason.
Levi- Its Biblical, Timeless and Old fashioned, a perfect fit. One of my four.
Isaac- I think this would be my fifth choice. It fits, but not as well as some of the others.
Rhys- It doesn't fit. Like Rowan, it really sticks out next to the others, it doesn't fit. Its pretty popular and trendy, while the rest aren't.
Felix- seems youneighkke, does not fit.
Jude- One of my four. Its old fashioned and doesnt stick out, fits well.
Ezra- would be my sixth choice, it fits but not as well as my other choices.
Quinn- same as Felix.
Jack, Avery, Levi, Jude, Paul, Jasper, Henry, Arthur, and Finlay really sound nice together and go together perfectly. I honestly don't think Klaus, Theo, or Lucian fit in. I think you should switch them out for Isaac, Ezra, and another name. They really don't fit and stick out.