Do you want a machine just for piecing, or will you be wanting to quilt on it also? I have a Bernina 350 which has performed flawlessly (piecing) for two years, but there isn't enough room between the needle and the right side to quilt anything wider than 4 to 5 inches, such as a border. I have a Janome 7700 for quilting and have just finished a king-size quilt. The 6600 is older, so maybe it is being phased out. Most of the major brands have shrunk the size of their "standard" machines and now seem to be focusing on sewing/embroidery models as well as long-arms. Seems to me, after nearly 70 years of sewing starting with a treadle machine, that there are so many choices that decisions are harder to make than ever. Best to find a good dealer who will support your choice whatever it may be. Happy sewing!