Will those drivers work very well on reasonably powered Nema 23s? They are only rated at 2A Absolute Max, and overcurrent protection kicks in at 2.1A. That being said, I run my machine at roughly 1.8A on the motors. These may be able to pull that off, but I would think you will still need some good cooling to do so.
The DRV8825 is a direct replacement on the CNC shield, and is rated at 2.5A Absolute Max with overcurrent protection coming in at 3A. You'll still want some cooling (fan and heat sink) on these, but I've run mine on short jobs without it.