I've built a rear Kinlin 300 onto a Novatec Superlight hub, 24 spoke, Sapim Race 2X DS (120kg tension) & Sapim Laser radial heads out NDS & it seems quite OK but possibly not as laterally stiff as I expected.
Comparing it with a Ksyrium Elite which has a much shallower rim & only 20 spokes, which would or should be the stiffer?
A wheel built with XR300 rims and 24 spokes 2.0-1.8/2.0-1.5 must be as stiff as the Ksyrium Elite. The handbuilt wheel will feel way more lively/responsive though.
First because it would be lighter, and second because the even spokes tensions make the wheel feel better contrary to factory built wheels.