Hi, After doing a little research on the Audio Physic Tempo III I found these speakers will take 180 watts at 4 ohms.
From the reviews I read most people were using 150 to 200 watt at 8 ohm amps. It would seem that your amp may not have enough power.
In amps, when you reduce the resistance you make the amp work harder because at 8 ohms you get 50 but at 4 ohms you get 75 watts. The resistance is called nominal which means nominally at 4 ohms but it will vary a little bit depending on load so this speaker could go down to 3 ohms at times.
As Newbee states If the impedance of the speaker remains above 4 ohms... well these are 4 ohm speakers
Anyway I would just contact both Audio Physic and Blue Circle and ask them about matching these two products.
Audio Physic's web page was no help in this regard.