Thanks so far everyone,
Ingo is right about the amount of files: right now we process about 25.000 files per day (14hrs) on 30x E3-1275 v5. 
We use Xeons because of the ECC support, which is a must for future processors.
The PP3 workflow is something like this:
- Demosaic
- (For some camera’s Flat / Dark field corrections, Lens corrections)
- Exposure comp.
- Color management (input profile)
Camera’s used: PhaseOne/Leaf/Canon/Nikon