Kappa & Givi are made by the same firm. They use the same fixing system so if buying secondhand bear this in mind as you might be able to mix & match depending on what's available.
I've used Givi kit for 15 years and have been very happy with their stuff. I'm currently using a Monorack and E46 box on a 1150GS. The Monorack fits to the panier rails which spreads the load to the rear frame rather than taking it all on the grabrail subframe. I also keep the original grabrail. Of course, I can't use hard panniers as the rails are taken by the Monorack: I'm a big fan of throwover panniers anyway, as they make filtering easier and discourage you from taking too much non-essential bollocks on holiday...