Sonic Frontiers Power 2 with Kef Reference 205

Which is the correct impedance to use for Sonic Frontiers Power 2 ampli with the Kef 205 Reference loudspeakers?
What does Kef state as the impedance for the 205 speaker?
8 ohm (3,2 min)
But the diagram of the impedance shows different things....
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That amp has pretty low output impedance since there are 4 output tubes per channel. The 4 ohm taps are a definite but if you have 2 ohm as well (not sure if it has them), you may want to try them and see what you think.