That would be the safest route. However it doesn't mean that you can't optimize each kit.
Take out the Corsair kit, run your Kingston kit, at it's recommended speed and timings. Test for stability.
Take out the Kingston kit, Add the Corsair kit. Now try to run the Corsair kit at the timings you tested the Kingston kit at. Test for stability. If the Corsair kit can run at the speed and timings of the Kingston kit, then you can have both kit run optimally.