Amps which are Great, but either Unknown or Underpriced

Though they've gotten several reviews in the last few years, I second Coda. They make really amazing stuff. No fancy bells and whistles--just clean, solid, no-nonsense engineering with terrific parts that work well together. 

I've owned several Coda amps over the years and currently own an S12.5, which drives my Jena Labs speakers very well. Really clean and super-transparent, with a touch of warmth that ties the whole package together. Lightning-fast but not overpowering bass as well. An acquaintance of mine has a 15.5 that powers a pair of Legacys, and that combo is magical too.

They're certainly not bargain basement in price, but for what they offer sonically, they're a fabulous value, IMO.

Several of Coda's principals worked with Nelson Pass at Threshold back in the day. As I understand it, after Threshold's demise, Nelson formed Pass Labs, while the other guys formed Coda. 

Coda maintains a much lower profile than Pass--at least in the press--but they've done a lot of OEM work over the years, including for Innersound, Legacy and Sanders (thus some of the similarity). 

I'd vote for Audio Analogue great sound for not a lot of money.

AirTight ATM1. Can be run as an integrated with 2 inputs and you can use them later with a pre or phono pre. You also can add a second one for monos for driving big or unefficient speakers.
They sound gorgeous. Art Dudley's ref amp. I have pair of ATM 3 for over 20 years and only one trouble fo fix one one amp.