Add up the prices for all of the components you will need, then double that number to get what it will actually cost. I'll bet that 1.5" ballscrews and 35mm rails are not gonna come cheap. You also probably want to re-evaluate your choice of spindle, its not only about speed, you also need rigidity. After I had spent this much money on a machine, I wouldn't be using stepper motors, I'd use AC servos.
After all this, plus your time (lots) it would be cheaper to buy a used machine and happily start cutting parts. You would also have the advantage of professional components, a tool changer, support from other users of similar machines, etc.
If the journey is the destination, then go for it, but if making a machine is just a means to an end, I would be looking at used equipment.