Have you tried Aurifil? I used Mettler silk finish cotton thread until I tried Aurifil 50wt 2-ply. *Much* prefer the Aurifil! A lot less lint, plus more fits on the bobbin so less bobbin-changing required.
Edit: Not sure about the best place to buy, but I have used
http://www.redrockthreads.com for discount thread purchases. They carry both Mettler and Aurifil.