The smoothest amp you've heard?

What's the smoothest amp you've heard? I'm talking something so smooth it was perhaps too smooth, if that makes sense
from a sonic perspective "smooth" doesn't present itself as something I am attempting to ascertain, or looking for in a amp? I have listened to many amps, I never recall saying "that amp is so smooth". I'm not trying to sound disrespectful. I think its a useless adjective when evaluating sonics of a component. Do you think a sound engineer says "we have to do it again, not smooth enough" IMO, Its a pointless term.
@jakesnak  Its not. In fact, if the amp isn't sounding nice and smooth, to me its an indication of higher ordered harmonics and I will be looking for a reason to work on the circuit 'till I have it right. It sounds to me like you've not experienced an amp that is actually smooth. My recommendation is to listen to the difference between a solid state amp and a tube amp (one in good condition of good design; not something hauled from a 1960s console...). If you've only heard solid state, you might have heard hundreds of them and not heard anything to justify the term. There are smooth sounding solid state amps but they IMO/IME are quite rare.

One qualifier: When/if you are interested enough to do this as an audition, make sure both amps are happy with the loudspeaker used. If that is the case, you won't have any problem hearing this difference- its literally why tube amps are still around after tubes were declared 'obsolete' back in the 1960s. Normally when the prior art is succeeded, it goes away. But tubes are still in production; they have been 'obsolete' now for longer than they were the only game in town! That's happening for a reason and that reason is literally 'smoothness'.

The Luxman m900u SS amp is very smooth as posted above. I never owned it but I thought it was the smoothest SS I have ever heard. 

I own an very smooth amp myself in the KRELL K-300i. Most comments I have read on old KRELL do not use smooth as a descriptor. However, this new KRELL with the XD feature on the amps are buttery smooth. A very enjoyable listen. I use them on some bright headphones than are uber revealing,  a great match. The Luxman is warmer than the KRELL.
At prices I consider reasonable (something not costing tens of thousands of $$$) there always seems to be a trade off of dull and muddy to get smooth, or harsh and edgy to achieve detail and punch.
In the 80s I had a little 80/155 W. PSE Studio II power amp paired with a Audible Illusions pre. that, to me, was a beautiful combination of smooth, yet unveiled and detailed and dynamic without being harsh and edgy. At only about $500.00 it put to shame amps costing much more.
A couple that I can think of (somewhat reasonable in the used market) that fit the bill of smooth, yet dynamic, clear and detailed and with enough grunt to drive a larger set of Maggies - an Ayre V-5xe or a Bryston 4Bsst2 or cubed......Jim