I would decide on what features I desired in a machine and for what purpose I plan to use the machine. If you are going to quilt on the machine then you want one with a wide throat and even feeding. If you are going to do a lot of embroidery then you want one that you can hook up to a computer and download patterns. If you are going to do applique you want want that has stitches you like for that. Higher end machines have more options, but don't necessarily sew any better. I would make sure I get it from a local authorized dealer and they will bargain with you. Save what money you have left for fabric!
My personal preference would be a Pfaff. The IDT can't be beat. I have owned many models and wouldn't settle for less. And, no, I'm not a dealer or have any connection. hee, hee