You found Evan it looks like...
Keep in mind that the 6V pack is a plug and go in most situations and can take the torque of a std servo from 48oz to 60oz.
I have had a few Hitec-925's which are SUPER fast, and the centering was not an issue. The 645's are the beasts with torque but poor centering-
If you want a decent digital, I run the Hitec 5645's and they are super!