I use 50wt 2 ply on top and 60 wt or higher in the bobbin for piecing. At Tristan's the Genziana Cotton Mako is the same thread as Aruifil.
For big cones of white:
http://www.tristan.bc.ca/cart/produc...7&cat=7&page=1
For a hug cone of 80 wt Aurifil Black:
http://www.tristan.bc.ca/cart/produc...1&cat=7&page=2
The Genziana spools and big cones have more color options. Here:
http://www.tristan.bc.ca/cart/produc...&cat=49&page=1 and here:
http://www.tristan.bc.ca/cart/produc...&cat=49&page=1
Aurifil size 12 wt is like embroidery thread. 40wt is a little thicker then the 50 wt and shows up when fmq. You can't beat the price of the door crasher, Sylvia's choice and Grab bag prices.