Even with very heavy quilting on a King size one 5000 meter cone will go a LOOOONNNNNNG ways! I quilt on a LA and mostly only use 5000 meter cones and I have yet to use one full 5000 meter cone on one quilt and that is even when I used to wind my own bobbins from that same cone. Now I use prewounds. But unless you are planning on doing some very detailed quilting like is seen in show quilts I think one 5000 meter cone should be ample for both your top stitching and your bobbin.