To get everything you want, plus have an interface that isn't sluggish, you're looking at the high end of any streaming platform. Roku, Apple TV, FireTV, and Android TV all have higher end models, but a lot of them don't support bitstreaming audio to your AVR.
I have a few Shield TVs and they work great for what you want. Sure, $200 is expensive, but it's a LOT cheaper than building a proper HTPC. It's also much easier to setup and use.
A lot of cheaper devices run Android TV, but you'll have to look at their specific feature list to make sure they support everything you're looking for. I have the Google TV streamers and they work fine, but struggle with full quality blue-rays. Not sure if they bitstream or not.