I have an Elna 740 that I bought used (it was a trade in machine, actually bought it from a dealer off eBay, who I felt comfortable with after numerous calls/questions). It has been a wonderful machine, not picky with threads, needles, etc. Love the harp space for free motion quilting. I just adore this machine and hope it lasts me a lifetime!
People generally like their Juki straight stitch machines, but I'm a bit sour on Juki right now as I have a new DX5 that has already been replaced once, and the second one is not doing what it should (bought a second machine to use primarily for sewing, and a bit smaller so I can take to quilting meet ups and such). Granted this is a different machine than the straight stitch machine (though it gets high rankings also). I always thought I would have a Juki straight stitch machine, but whenever I tried one at the dealers on different occasions, I never really fell in love with how it felt when free motion quilting. Tension issues at the store that the dealer couldn't seem to adjust, the feeling of the quilt sandwich not moving freely - each time I tried.
Which is why I would highly recommend that if there is any way you can test all of them, definitely do. Machines feel differently, and you want one you like the feel and sound of. What is someone else's cup of tea might not be yours.
All that said, I think from between your 3 choices you will end up with a great machine!