Pretty much the best place I know of for modding info is: http://www.xbox-scene.com/
They have a lot of links for buying new mod chips. I've been out of it for a while... I have an Xecuter 2, but I guess the 3's are out. I, and a friend of mine, both ordered our chips from http://system-mods.com/
I have no idea what MS's design plans for XBox 2 controllers are.