I tried to find the Sopra 2 imedance curve but I couldn't find anything. If the impedance drops down low (2 ohms or so) for much of the audio band then you would need a very robust amplifier for them to sound their best. Your Anthem is rated for 2 ohms and increases its power with each halving of the impedance (400 @ 8 ohms, 600 @ 4 ohms, 800 @ 2 ohms) but it does not have the balls of a Krell or other monster amp.
Assuming that the Sopras have a reasonable impedance curve then your Anthem should work very well. You would have to spend huge bucks to get an amplifier with more current than your Anthem.