Givi v Kappa v Nonfango

Can anyone tell me whether all three models of top box above are interchangeable- ie if I have a Givi monokey base plate for a top box can I use all three makes?

Being a cheapskate I am doing some research into the most cost effective option and before I spot anything on Ebay or similar, need to know whether they are all interchangeable

Any advice / brands to avoid greatly appreciated

Givi and Kappa are made by the same company and are interchangeable

I have a nonofango 848 topbox including the mounting plate which I would like to sell (used on previous bike) its in very good condition.

If you are interested please contact me at ianm00@bigfoot.com

Thanks

Ian