I think it's important to establish your price range first, and then the features that are ***really*** important to you. For quilting, one of those features might be a larger harp size. Other often-cited ones for quilting are needle-down and auto-cut. Vikings have an auto-lift feature that sounds absolutely wonderful for machine applique.
One of my most important features, that I don't often see mentioned, is the quietness of the machine. My Bernina 1230 just hums; I would not be happy with a machine that clanks or whistles! But that's me
Try out as many different machine brands as possible. Because quilting is important to you, prepare some 3-layer sandwiches to take with you so you can try out quilting on each machine. Also, bring some strips of your own fabric to piece together. This helps you assess how straight fabric feeds and how good the stitch looks. Dealerships supply you with fabric that has been starched to the hilt because stiff fabrics hide a lot of minor flaws in stitch quality.
Sewing machines are like cars. The "feel" of different brands is different, and everyone has a different idea of what's important.
Edit: State fairs and quilt guild shows are often good places to go to "test drive" different machines. Also, fair and show prices are often the lowest prices you can get from local dealerships.