Looking at the Lyr, it can be used as a preamp to connect to a normal amplifier. It has stereo RCA preamp outputs on the back and they are controlled by the volume knob.
I'm not sure why Snell is recommending 100-300 watts. The speakers sensitivity is 87db which is actually pretty normal for an audiophile speaker (typical is 87-89). Only specially designed speakers are more efficient such as Tekton or JBL or other (like in the 95db to 98db area).
If you plan to use the Lyr (which would be a really nice tube preamp), there are lots of power amp choices. If you want Class D, look at Nord One UP (they are made in Europe). Otherwise, Bryston if you want a more exacting sound (similar to Class D) or something like Parasound A21 if you want something warmer and more engaging. Many other choices. It's easy to hit 200 watts per channel with an amplifier.