When it comes to Android TV streaming boxes, there are really only two options: the Nvidia Shield TV, and if you're not playing games, the Xiaomi Mi Box S. Now you can grab the entry-level Xiaomi box for just $35, a drop of $25 from the original MSRP (though it has gone for $40 a few times in recent history).
The Mi Box S supports video playback up to 4K (with HDR support), and the voice remote enables you to use Google Assistant to open apps, start playing a specific movie, or anything else. It can handle pretty much every media streaming app available for Android TV, though the CPU isn't really powerful enough to handle gaming.
The main catch is that the Mi Box S is still running Android TV 8.1. There's a beta available for Android 9 Pie, which includes official support for the Amazon Prime Video app, but the stable release hasn't arrived quite yet.