Nice looking, but something smells funny with their performance vs pressure drop graphs:
If I'm reading that right, the PolarFlo TT apparantly has a pressure drop of 0.5mH2O at 20LPM.
Slap me silly and call me a skeptic, but 1/2" ID tubing attached to a 1/2" OD barb with 10mm ID has a pressure drop of around 0.80mH2O all by itself, and that's not even including the pressure drop due to the inner structure of the block, or the water that has to exit the block.