[wrxtasy]

So if I take a browser out of the equation (mis-read in my initial search and thought Chromium would run on it), where does that point me? I've got an HDMI cable I run on demand from my main PC to the theater, was just trying to eliminate that need, but I'd rather keep using that approach to go with a compact and easy Kodi box. Same with 3D (which I added in an edit).

Please re-read Post No.1 of this thread again. There are a bunch of Frame Packed 1080p 3D specific devices in that.

99% of normal Kodi devices will do Half resolution Top/Bottom / HSBS 3D.

You need Ethernet for 4K video streaming reliability.

If you want a Hands off box that does 1080p/4K Auto Resolution switching for optimal picture quality on a 4K TV then avoid Android all together.
Otherwise be prepared to fiddle with settings.

Already given some - 4K / HD Audio media player options in this post:
AMLogic S905(x) - LibreELEC / OSMC - Kodi Krypton - 4K Options

Be aware ARM devices running from a microSDHC card / eMMC will not be as lightning quick as a full blown PC with Top Spec SSD storage.
They are by no means slow at all. You are not paying much in comparison anyway.