Amps which are Great, but either Unknown or Underpriced

I second Quicksilver Audio   I have a pair of Mid Monos and I love them. One of the true values in audio.  

I will add my 2 cents worth and say Odyssey falls into this category.

The Yamamoto A08S 45 Single Ended Triode Tube Amplifier is gorgeous with a pair of 98db sensitive Lowther PM5A (Alnico) drivers in Open Baffle. It is hand-made and illuminates textures, detail, transparency, a haunting sense of 3-dimensionality and captures the ambient 'space' of where the recording was made. It also has that mysterious sense of 'flow' that helps bring music to life. Srajan of 6-Moons suggested it sounded more tonally richly saturated than a 300B tube SET amplifier. He was right! It is also uncannily quiet. Shigeki Yamamoto is a master. It should cost at least $8,000 but only cost a ridiculous $2500, helped by the currently strong US dollar. It is also beautiful designed. There are few audio amplifiers that come even close to it as a work of art.

Agree on the Belles - still use one f his first, a Belles A, in a third system

The Juicy Music Audio pure class A Triode (pCAT) monoblock amplifiers are outstanding.  Unfortunately, they are discontinued, rare, and don't come up for sale often.