I like Aurifil 50wt 2-ply variegated thread for quilting, but I think it is considerably thinner than King Tut (which I haven't used). I like it because it is very smooth, creates almost no lint, and because it is a fine thread the bobbin holds more of it (so I don't have to change the bobbin so often). I use this thread for piecing also. My machine loves it, and I love it!
If you want to try out Aurifil,
http://www.sewezdesigns.com is having a terrific close-out sale on it for the rest of May. It is only $6 per spool, so is a really good deal if you buy multiple spools. My LQS carries only a few colors and charges about $11 per spool.