I'm talking about using one of these android boxes and connecting it to a monitor, a pair of computer speakers, a mouse, a keyboard, etc. and using it instead of a standard Windows PC for watching movies, listening to music and also for surfing the internet, sending and receiving e-mails, playing some video games, reading and editing documents and images, etc...
Is this feasable, and what would be the best android box for this?
Not AndroidTV per se, but any of the android boxes that runs full Android would most probably accomplish your needs.
Raspberry pi would be much better for this and probably cheaper.
if you can do those things with your (android) phone, then yes..
Chromebox depending on your editing software... Also, look into mac mini box if it doesn't have to be android or windows.
I wouldn't do this. Better option would be to get a Raspberry Pi, throw Raspbian on there, and use that.
I wouldn't recommend an Android box for anything, and I also wouldn't recommend an Android TV device as a PC replacement. Buy a phone and a Chromecast or get a Chromebook or a Chromebit.
Get a Chromebook or Chromebox.
Don't waste you time with Android trying to do PC type activities. It will be a frustrating, compromised, underwhelming experience.