The crossover frequencies for the replaced midrange will be incorrect. It won't affect the other drivers, though.
But what exactly do you mean by this: Infinity RSM with a Kappa 7, 4 Ohm crossover? Have you replaced the crossover in your RSM with a Kappa 7 crossover? Why on earth would you do that? Crossovers, except in the cheapest speakers, are part of the design of the system. Swapping in a new crossover (either a generic or one designed for a different speaker system) will work, but not as designed, for a multitude of reasons I'm not going to mention, but this has been discussed many times here. It's unlikely it would be an improvement over the original if the latter is working properly (and if not, it's better to repair the crossover rather than replace it).