Very useful guide, thank you for putting that together!
Juki's weren't mentioned but they can be pretty awesome.
Something to look for: not all machines have straight stretch stitches. If you plan on sewing loads of spandex, this is a must. One of my machines is a low-end Singer with a great selection of stretch stitches and I use that machine for superhero spandex suits the most. If you never plan on using super stretchy material, then this is not something you need to pay for.