Random Thoughts.....What Are You Thinking?

I don't think the steam machine would be much of a upgrade to what you've listed. I'm pretty sure currently is not a good time to buy a new one either, AI bubble needs to pop first I'm afraid.

If you bought a pre-built PC chances are they saved at stuff like fans or power supply so maybe just look into better/silent fans once you're sure it's the fans and not the hard drive for example.

*edit*
I don't get the appeal of the steam machine. I read people want it for the form factor so they can place it next to their TV and play in the living room. Imho TVs are so flat and large by now that I wonder what's stopping people to just "hide" a regular PC behind it.