Anybody heard the AR Reference 210 Monoblock
 

Any thoughts?

Very nice amps. I've heard them driving Wilson Alexias at a friend's home. Drove very well to reasonably loud levels. Not the best at controlling the bottom end but very nice nevertheless.

What the bottom fat and slow? Flubby?

Not as tight and fast as the Ref 250s or the GS 150. However, it is a very musical set.

I had the Ref 210s in house for a test listen. Frankly, I believe the Ref 150 or 150se is a more musical, realistic and powerful sounding (although not necessarily more powerful) amp with a much better bottom end and much more palpable images . The Ref 210 had better imaging/soundstage, but not by a lot. I found the Ref 210 a bit too diaphanous all around with bottom end that was a bit thin and wispy for my taste. The latest generation of amps was a huge step up.