So you guys all agree that the HD 7850/GTX 560 is equivalent to PS4's GPU?
If that's the case then we're gonna be eating good on the Sony side
that site gives those specific GPUs a 10/10
Radeon HD 7850 PC Gaming Graphics Card Hardware For Game System Requirements
GeForce GTX 560 Ti Twin Frozr II/OC 2GB PC Gaming Graphics Card Hardware For Game System Requirements
I can't say what graphics card equivalent it is, and you can't really compare them anyhow since due to the closed nature of the system, much more performance will be able to be extracted compared to a pc with similar specs.
If you're not willing to build a monster rig, ps4 will be more than sufficient to get you through. You might start seeing significant advantages on the pc side in a few years time, but for the first years or so, pc will mainly be higher framerates and resolution and possibly physics given you have a monster rig to outmuscle the PS4 rendition.