i think it depends on what you want to do w/ it. Are you just piecing on it, or do you machine quilt? Do you like to do machine embroidery? What are the other things you might sew on your machine?
Now go and look for one. A used machine found on craigslist would probably allow me to get more of the bells & whistles that i might not normally look for.
I personally love my old Singer Fashionmate - it's heavy duty and i am fine w/ just straight and zig zag stitches..