The speakers handle at most 200W, and the amplifier will put out 200W before distorting heavily/reaching its limits, but you're unlikely to actually listen at levels that need 200W. The KEF 104/2 has a sensitivity of 92dB @ 2m @ 2.83V.
Assuming the Sphinx V2 has enough drive (the speakers are 4 ohms nominal, which means they may dip lower, and they may also have some difficult phase+impedance points), you'll probably only use a few dozen watts at the most unless you are sitting very far away or are trying to damage your hearing.
Assuming the Sphinx V2 has enough drive (the speakers are 4 ohms nominal, which means they may dip lower, and they may also have some difficult phase+impedance points), you'll probably only use a few dozen watts at the most unless you are sitting very far away or are trying to damage your hearing.