I've not tried to buy this exact product, but have had problems using AmiStore a few months ago.
It was impossible to make a purchase, because my shopping cart would never empty. When I got to the point of paying, I had like 5-6 identical products in the cart. When logging in on a later date, the same items were still there, but they did not show up in the cart in AmiStore. Tried different things to fix it, but to no avail.
Contacted A-EON several times, but got no reply. The result was that I ended up ordering a boxed version of Enhancer instead.
It would be nice if they had a shopping section similar to the usual AmigaKit website. Would be much easier!
Maybe a system similar to Alinea in Germany? I've bought downloads from them and it works very well. You put the wanted software in the cart, check out and pay, and then you will receive a link to download what you've bought.