Which UCD*HG for my KEF Reference Model 2

[Groucho2004]

I'm about to pull the trigger on a couple of Hypex UCD modules for a stereo power amp. My KEF Ref 2 (original Reference series) are 4 Ohm but dip down to about 3 Ohm in one or two places. However, sensitivity is rather high with about 89-90 dB/W so I won't need that much power.
The distortion figures of UCD 180's look a bit better to me than the UCD400's but can they easily drive my KEF's?

Any advice is appreciated.