I've just re-read the first 8 pages of this excellent project and the subject of spindle power was discussed in depth, i would tend to agree that using a small spindle will be limiting its use, I would be looking at a decent BT or INT taper spindle with tool change ability and a large motor maybe 7-8Kw and possibly a two speed pulley to give maximum speed range or the choice of steel vs alloy machining etc. ;)