You want to know what you want your machine to do well...what stitches are a must, then try those things out on the machines you look at. Spend as much as you comfortably can so you can get the best machine for your investment. Hopefully wherever you buy your machine will give lessons, and offer service and followup advise as you need it. I do have a Bernina that I bought over 20 years ago, for almost $2,000 and it still sews like it was new, and I use it a lot. I love the blanket stitch that it has, as well as the feather stitch.
I also have a Brother PQ quilting machine-only sews straight stitch...it has the larger throat area...sews very fast so also good for machine piecing-especially strip piecint. That was under $1,000. I mostly use it though, for machine quilting.
Good luck, and hope you find a machine that you love and lasts you for years!