Parasound Halo Integrated vs Yamaha AS2100

warm and inviting=Parasound.

The Parasound is the warmer amp, at least compared to the A-S1100 (A-S2100 sans balanced inputs?) 

I don't believe you can get anything better than the Parasound Integrated under 3k. Getting back to the original post either of the 2 options would be able to drive the the Motion 40s. The Parasound would definitely have an edge as it has almost double the power and lots of current. When I first auditioned mine, the store had it connected to a standing Monitor Audio  (similar specs to the ML). The Halo Integrated drove those speakers with such authority. Safe & Sound's owner Mike let me listen for about 2 hours. After that I had to have it! The amp still puts a smile on my face, especially the other day when I played the new CSN MQA remaster of "Suite: Judy Blue Eyes". I can't recommend this amp enough. It actually got me curious about what the halo JC separate components are capable of. 

If you decide to broaden your options, I strongly recommend to consider Vincent Audio SV-237 tube/hybrid integrated amp. It sounds incredibly detailed and smooth and completely free of any graininess even at very high listening levels.

You might want to check out newrecordday. I think he has reviewed both.