Finaly managed to get 3 boxes working out of the batch I had and now seem to find the following issues:

Lots of errors like
 [2014-06-25 06:49:08] KnC: 3.0.310 Failed to setwork (19)
 [2014-06-25 06:49:08] KnC: 3.0.311 Failed to setwork (19)
 [2014-06-25 06:49:08] KnC: 3.0.312 Failed to setwork (19)
 [2014-06-25 06:49:08] KnC: 3.0.313 Failed to setwork (19)
 [2014-06-25 06:49:08] KnC: 3.0.314 Failed to setwork (19)
 [2014-06-25 06:49:08] KnC: 3.0.315 Failed to setwork (19)
 [2014-06-25 06:49:08] KnC: 3.0.316 Failed to setwork (19)

And hashrate drops to almost 400Ghash when running into a lot of hardware errors.

 [2014-06-25 06:50:01] KnC: 1.0.344 disabled for 300 seconds due to repeated hardware errors
 [2014-06-25 06:50:01] KnC: 1.0.349 Failed to setwork (99)
 [2014-06-25 06:50:01] KnC: 1.0.349 disabled for 300 seconds due to repeated hardware errors

Another thing I noticed is that these boxes seriously overload a multirail power supply on startup and causes the power supply to shut down even with enermax 1500W power supplies.
Already send in a report with KNC awaiting their response.
Very unhappy at this point