Hello and welcome to Support Forum.
First of all, thank you for your interest in AmiKit!
Here's an explanation about AmiKit versions:
AmiKit 8 is the latest free version of AmiKit.
AmiKit X is a paid edition - there isn't any discounted upgrade archive for AmiKit 8 users. Simply AmiKit 8 was free, AmiKit X was paid (29.95 EUR).
AmiKit XE is the latest (and greatest) paid edition. Full installer is also 29.95 EUR. But if you bought previous AmiKit X, you can purchase the upgrade archive for 19.95 EUR.
If you want to use AmiKit XE without having the X version, simply purchase AmiKit XE full installer for 29.95 EUR.
But if you already purchased XE archive without having the X version, please purchase full XE installer instead and I will refund you for the upgrade archive.
Hope it helps,