17 points would be way to cheap for a fast and hard hitting 1+AS unit. Several elite infantry costs 15 points like white lions, chaos warriors, swordmasters. No one of the gets better AS than 5+ for those points.
A drop to 20 or 21 points looks fine to me. May be it would better to give them a free +1 S and keep the points at 23 points. Imho it is the wrong way to reduce all points of cavalry. Cavalry should get more hitting power.