Or maybe they'll have a minimum spec that gets bumped every 2 years, so a game can say "runs on all Steam Machines (2014+)".
But it's clear there's going to have to be some way of "tranching" the different hardware levels, because nothing will kill this idea faster than a general public who's heard that you can never be quite sure if a game you buy will run on your particular Steam Machine.
But then I realize something: where do people get Steam games from? The Steam store online! I'm pretty sure they'll build in the equivalent of the windows performance score that can be sent to Steam's servers, and they'll simply be able to show you the games that will run best on your machine and hide games that simply won't run at all.
Thoughts? I think that, as with the controller, this is a really important aspect of getting this whole big idea to work.