I can't comment personally on any of the machines you are looking at (I have a Bernina 153QE, LOVE it, although all metal so heavy), but wanted to give you one more thing to think about. On another forum, there's a gal who just bought the Quest for $700, as it is being discontinued for the new and improved model. Like you, she found little difference in the actual machines. But as it is considered discontinued, the dealer was willing to give her a great deal; perhaps you could find a dealer willing to do the same.
Good luck with your choice!