I was planning on going the Sherline route as well but heard some rumors that the quality was down a bit and that backlash could be significant on the workpieces of the size I'm planning.
I started investigating DIY harmonic drive setups when I stumbled across this. The vendor told me via email that he's willing to remove the chuck and even the stepper to drop price and shipping cost. I need a four jaw since I'll be unsung 4" x 3" stock but I might buy with the 3 jaw just to have if I actually go for it.
-Andy B.
http://www.birkonium.com CNC for Luthiers and Industry http://banduramaker.blogspot.com