I agree with Raks that it would be best to present the question to Gamut. You should indicate to them that you are using Kef Blade speakers, and also the length and the capacitance per unit length of whatever speaker cables you are using. If the capacitance per unit length of the particular cable is not specified, before contacting Gamut it would be best to contact the cable manufacturer and ask them if they can tell you. But if that can't be determined, at least indicate to Gamut the make and model of the cable, as well as its length.
I couldn't find an impedance curve for your speakers, btw, which might have been helpful because a plot of impedance phase angle vs. frequency would provide a feel for how capacitive a load the speakers are at various frequencies.
Also, ZD is correct that reducing the gain of the amp by means of the internal gain select switches, that are described in the manual, will tend to minimize the chances of a problem, ***IF*** the gain select function is within the amplifier's global feedback loop. I would guess that stands a good chance of being the case, but not having specific knowledge of the design I can't say that with any certainty.
Everything else being equal, the chances that an amplifier using feedback will break into a potentially destructive oscillation are increased as its gain becomes higher, and if it is asked to drive a heavily capacitive load.
Regards,
-- Al