Welcome Mal - from Chicago(ish)
I too had bought a machine that was a good all around sewing machine. Then I discovered quilting and my machine wasn't exceptional at it, and again, like you, I found the Janome 6600. My first machine was only 3 years new so despite having the $$ available for the 6600, I couldn't "justify" spending a few thousand on *another* machine. I lucked out and found an "experienced" 6600 at my dealer shortly after the 7700 came out and several people had traded up to it.
Check with your dealer, and other dealers within a distance your willing/able to travel. Get on a waiting list for "experienced" 6600's. Ask about trade in, but you might find that 2 machines come in handy especially if your first machine does something especially well (my first machine is a Huskvarna and it sews heavy material exceptionally well so I can justify keeping it - using it today in fact).