Oculus website has system specifications for "the full Rift experience" when they release their Oculus Rift VR headsets next year, saying: "All of the games and applications for the Rift created by Oculus will provide an incredible experience on this system." They also now offer a new version 0.6 of the PC SDK, and here are the release notes for that. Here are the recommended specifications:

The Rift’s Recommended Spec
Presence is the first level of magic for great VR experiences: the unmistakable feeling that you’ve been teleported somewhere new. Comfortable, sustained presence requires a combination of the proper VR hardware, the right content, and an appropriate system.

For the full Rift experience, we recommend the following system:

• NVIDIA GTX 970 / AMD 290 equivalent or greater
• Intel i5-4590 equivalent or greater
• 8GB+ RAM
• Compatible HDMI 1.3 video output
• 2x USB 3.0 ports
• Windows 7 SP1 or newer

The goal is for all Rift games and applications to deliver a great experience on this configuration. Ultimately, we believe this will be fundamental to VR’s success, as developers can optimize and tune their game for a known specification, consistently achieving presence and simplifying development.

All of the games and applications for the Rift created by Oculus will provide an incredible experience on this system.

Binstock, Oculus chief architect, wrote a detailed technical post outlining the recommended system specification and the reasoning behind it, along with more Rift details, here: “Powering the Rift”.