Hi Cyril and welcome back! Short story:
AmiKit 8 cannot be upgraded to AmiKit X. The newest X version is a brand new installation. But both versions can coexist on the same computer (providing you install the new one to its own separate folder).Long story:
AmiKit X was originally developed for (and on) ALICE laptop as its main operating system. Even though AmiKit 8 was used as a basis for new AmiKit X, an update archive was never planned. There was no need for it as there was no ALICE laptop with AmiKit 8 that would need to be updated, of course
Later, when I was thinking about to release AmiKit X even outside ALICE (because the laptop project got delayed), there were SO many changes in the new version that creating an update archive for AmiKit 8 became impossible.
Yes, AmiKit 8 can detect the update on the server and then it displays "download it manually" message. This text was originally reserved for "manual" updates which were able to update things outside of AmiKit, for example WinUAE.exe. In case of AmiKit X "update", the text is a little bit misleading, I know, but it cannot be modified.
Anyway, if you decide to purchase AmiKit X, you will get a brand new and shining AmiKit with MANY new features. On top of that, unlike AmiKit 8, the new AmiKit X is being constantly developed. 3 free updates were released since its initial public release