It depends on what you plan to do with it and what machine(s) you all ready have.
I think the new Janome 7700 is overpriced right now because of the hype. You don't have the Viking Sapphire on your list and it was selling for $900 at Paducah which I thought was an excellent deal.
There is also an Elna 7300 which is very similar to the Janome 6600 on your list.