I like the specs for the first 300 prototypes, but it is purely for testing. I wonder what they will go for eventually, but my guess is 760 with an i5 because hyper threading is needed so much while gaming (?) given that is pretty much the biggest reason for an upgrade jump between i5 and i7. Someone more knowledgeable can maybe discuss this further. Other than that it is pretty much standard, 16gb ram is good for future proofing, as 6gb is minimum for example Watch Dogs (what?). The thing that is bugging me is the HDD vs. SDD. You can really feel the difference in loading times on a SSD, two easy examples are TF2 or Planetside 2, which absolutely fly on a SSD. Having a HDD will probably worsen the user experience of the Steambox, however it can probably be upgraded manually after buying it.
I can see three different final specs for the Steambox, one budget that is purely for the streaming service and "light" to "medium" living room gaming, then the top seller which is a mix with good enough specs and focused on "mid-high" gaming experience, and then you have the killer spec which totally breaks the bank for the hardcore gamers out there, professionals and whatnot.
EDIT: In regards to the controller, the functionality is really interesting and forward looking. However the controller itself is ugly and I wonder how it feels. Furthermore, during the FPS demonstration you can really see how it doesn't quite stand agains the traditional mouse in forms of speed and accuracy, but who knows, it might require some training to get that top notch skill with that controller, so I won't be negative towards it just yet.