I don't think the hardware spec will be fixed. The article seems to think it will be Android-like. Valve will give guidelines like 'must support OpenGL' and 'needs at least HDMI output and 6 USB ports', but if you want to spring for the Alienware Mega-'Console', then you'll have a bit more power.

And the more I think about this and type my response, the less exciting this sounds... All of this is possible on a PC. What they'll be offering us is basically a pre-loaded, locked-down Linux based OS.