Shaggy, here is one link to a discussion we've had about sewing machines. There may be others that you find on your search, but you could start here...
http://www.quiltingboard.com/posts/list/116.page
I think it's great that you want to get her a new machine for Christmas. She's going to love that!! In the meantime, has her current machine been serviced lately, or have you done any maintenance on it yourself? Sometimes just a good cleaning/oiling can make a huge difference. Especially in the bobbin area. That seems to be the one place that my machines have needed some cleaning and a little squirt the most often.
Her quilt is just beautiful! :)