I would consider splitting up the money in order to get a separate machine for embroidery. That way you can be piecing or quilting on one machine while the embroidery machine is working away on a design.
For quilting, a bigger harp (area underneath the arm) makes it easier to quilt a large quilt. A lot of quilters like the Janome 6600 because of this, plus it has lots of embroidery stitches and other features.
Keep in mind that "best" varies from one quilter to another, just as the "best" automobile varies from one person to another within a given price range. There is no substitute for actually sitting down in front of a machine and doing those things you like to do with your own fabrics. You can see how responsive the machine is, if the stitch quality is what you want, you can tell how loud the machine is, etc.