I worked for Viking Husqvarna New Business Development inside a JoAnns for a while. My guess is that the dealer "chooses" not to match a price - she does have that amount of flexibility on the price but chooses to have a greater profit. My recommendation is call another dealer just for a comparison. On the up side, she will deliver (if she is a good dealer) support, classes and warranty support - which for some sewers that type of support is essential. Question is - Is that support worth $600 to you? As someone else commented that $600 almost purchases another machine.
Patrice brings up several valid points about returns, refunds, restocking and repair.Make sure that you know all the ifs ands and buts before you click "buy" online. I know several online friends who have purchased from AllBrands and have been very happy. They are a HUGE sewing machine seller from Baton Rouge LA and their price is about the same as you quoted. Just note ,that generally once it is delivered it is yours.
I agree - if you have the time and will be near a show look there. I, myself, would start by calling all the dealers within 4 hr from my home. I might even call Juki and ask about how warranty work is accomplished on machines purchased online. I personally would not hesitate to purchase one online. Always remember - an informed purchaser is a happy one - lol. Best of luck with your choice.