I ordered several skeins of Weeks Dye Works 6-stranded floss online from Ribbon Rose.
I adore the shades available and although they are quite expensive, if you want your piece of art to look classy and have an interesting textured look then use this brand. The dying is excellent giving subtle variations is shading throughout the skein.
I also recommend The Ribbon Rose for their ability to always attend to my online orders immediately and delivery is swift and priced very fairly.