Class d amplification

The KEF has a sensitivity rating per speaker of 86.8 dB@2.83V/1m

a minimum impedance modulus of 3.3 Ohms at 40Hz, 150Hz so they're gonna be current hungry speakers.

so you need a high current amp that can get to sustained 80dB average SPL from your seated position (assuming 10ft from the speakers) and instantaneous transient peaks of roughly 100dB.

Plugging that into this room calculator with an amp of power delivery of 700 Watts means we get to 105.6dB at your seated position.

This is the monoblock in question - Hypex NC1200 Premium Monoblock Amplifier Apollon PNC 1200

It does 1200W into 2 Ohm, 700W into 4 Ohm and 400W into 8 ohm.

get two @digitaljoseph 

Only a two year warranty is somewhat concerning , no?

@digitaljoseph   I'm very happy with the performance of a pair of Atma-Sphere GaNFET Class D monoblocks driving Aspen FR10 speakers. The sensitivity of the FR10 is 86.5 dB, which quite similar to the KEF and Joseph speakers you mentioned. The A-S monoblocks are incredibly transparent and power the FR10's planar tweeter and midrange driver with amazing realism and an absence of harshness. The low end is great, too, conveying impact and natural tone to drums and stand-up bass. 

I can't tell the difference between GaNfet class d and modern amps from Purifi and Hypex which cost half as much at twice the power. Even GanFet purveyors can't (won't) defend it. All they got is "efficiency" and "runs cool."  But that's common to all Class D amps so mn

Any Aavik amplifier will do, if you can afford the i-280 is the one to get.