Does anybody have any numbers like here that can help me what kind of performance to expect with multiple GPUs with the PRO version.

If I don't intend to use more than 2 depth sensors and I value overall throughput more than individual turn around time. then:

1. Is it better If I have two machines working at the same time than having a single machine with multiple GPUs?
2. Is it faster to track two actors at the same time than doing them separately one after the other?

Hi
Please read some general recommendations about multiple GPUs in our docs
http://docs.ipisoft.com/Multiple_GPUs

All in all I would not recommend you multiple GPUs for dual Kinect configuration. You'll barely get substantial increase in tracking speed. Overall throughput with 2 single GPU PCs will definitely be greater than with 1 dual GPU PC (assuming same GPU models).

Tracking multiple actors will be even slower than tracking one by one. However, this is for a reason - multiple actors tracking considers mutual positions of actors and produces more accurate tracking results with less tracking errors during the process. While for single actor tracking other actors in the scene are just additional noise in the picture.