Depends on the particular box. Low wattage, low cost models are going to be sealed boxes most often. I consider those to be analogous to consoles/Rokus etc. Except they will do more.

SteamOS will run on anything though, so obviously many people will still build elite level gaming towers.

The thing is By cutting out Windows, that right there knocks $100 off the retail cost which becomes huge when you start talking about 2 and 3 hundred dollar boxes, plus there is a lot of driver and other optimization going on right now. So once all the common apps come out of the box, plus all the crossover and new entries like we have seen on iOS/Android markets...

Steambox will do everything, and dollar for dollar MS just wont be able to compete.

For who could be free when every other man's humour might domineer over him? - John Locke (2nd Treatise, sect 57)