According to a Valve Engineer, the Steam Machine specs outclass the most common PC configurations. The company relied on its own hardware surveys to choose the system’s components. Even as an entry-level option, Valve claims that 4K/60 fps performance is realistic, despite a memory-limited GPU.
Possibly not, crysis is single thread bound due to it being a 32 bit application. You can technically run it as x64 but that’s cheating.