NEMA-17 is plenty for a 500x500x500mm foam cutter. Hot-wire cuts have almost no resistance — the wire melts foam, doesn't push it. The motors mostly fight friction and inertia, not cutting forces.
NEMA-23 makes sense if you're building a 1500mm+ machine where the moving mass matters more, OR if you want extreme speeds for non-foam materials. For everything else: NEMA-17 with 1.2-1.5A current, 0.9° or 1.8° step angle, both fine.
NEMA-23 makes sense if you're building a 1500mm+ machine where the moving mass matters more, OR if you want extreme speeds for non-foam materials. For everything else: NEMA-17 with 1.2-1.5A current, 0.9° or 1.8° step angle, both fine.