If it has a horn it has a crossover, so the different impedance will move the cut-off frequency of the woofer a bit, but not the tweeter, so it probably won't have a dramatic effect on tone. It may not even have a cut-off circuit for the woofer, not really necessary and it's rather costly.
The Kappa Pro is probably a more efficient driver than the original so you'll want to turn the tweeter up assuming you use it at all, but beware that it is *a PA driver, not a bass driver*. It does not have a high excursion capability, only 3.2mm compared to the Kappa Pro 15LF's 6.7mm. I would not push your cab with more than 250W. It's 3dB more efficient than the 15LF, so it will perform like a 375W cab, just takes less amp to get there.
If it's more than $200 don't buy it, you'll have trouble selling it if you don't like it.
SVP-CL + IPR 1600 + SWR Goliath III 4x10 = bliss