Personally, I would not go back to that dealer. I can't see that you got any benefit from them, and their prices seem high. I found the Janome 8900 on Amazon for $2,499 (free shipping with Amazon Prime) and, if you scroll down and read the answers to questions there, one person mentions she got it locally for $1,799. If you consider your existing Viking machine is scrap, you still get a better deal buying from Amazon that using it for "$1,000" worth of trade-in value at your dealership.
You could purchase all 3 machines from Amazon, try them all out at home, and then ship back whichever one(s) you don't prefer. To find out how much it would cost to ship each machine back to Amazon, go to Amazon (don't log into it, or log out of it, if you have Amazon Prime so you can see how much it will cost to have them ship it to you), add it to your shopping cart, and start the checkout process to see how much shipping is. Amazon is ***very*** good about taking returns if you change your mind, as long as you return within their time period (check, but I think it is 30 or 60 or 90 days). It's easy to return. Just go into your account, click on "return" for the item, and print out a packing slip and postage sticker for the box. They will deduct the return shipping from your refund.
Edit: You could always sell you Viking on eBay for scrap value.
Edit 2: Oops, sorry! The Janome I found on Amazon when I searched is a 7700. Personally, I would probably opt for the Juki machines anyway -- especially if my only option for purchasing the Janome is that dealer.
Edit 3: You have to create a free account and log in to read the full review (and there may be other reviews there), but this one lists her purchase price of the Janome 8900 as $1600:
http://sewing.patternreview.com/Sewi.../Review/1/5614
Here's another one that says she paid $2,000 for the Janome 8900:
http://sewing.patternreview.com/Sewi.../Review/1/5659
and another who paid $2,400. All 3 reviews were posted in 2015.