Looking for an amp that punches way about its weight and I can grow with

+1 to those who suggested Rogue. I have a Stereo 100 driven by a Rogue RP7. Amperex 7316 + Amperex Bugle Boys in the RP7, Amperex long plate 12AX7 + Mazda long plates 12AU7 in the Stereo 100. Speakers are Legacy Signature SE (4 ohm). There are times I can’t believe how good this sounds. Rich, detailed, spot on treble decay, bass for days if called for. I literally have no desire to change anything anytime soon. Of course most in this thread will suggest what they own or have had lots of experience with... guilty! I had a Parasound Hint with Tannoys before this. That was no slouch either, but holds no candle to my setup now.  I know one can get MUCH higher end amps, but I'm good for now, and indefinitely. Famous last words?

+1 Odyssey
Alon Wolf of Magico speakers likes and has used Odyssey amps.  Magico uses cutting edge technology and are among the best of the very best speakers available today.  

Unison Research Unico may fit the bill....I know where you can still get one NOS new in box, $2k...dynamic class A at first then 80 watts total. Two 12au7’s in preamp section, Italian made...a gorgeous integrated amp. 6 moon wrote up a great review on it, and it was chosen product of the year....its now 20 years old, but I’d take a chance with it with a good warranty....it preceded the Unico Primo....

Hi, Justin (OP) and all, 

Subject to... your system, ears, preferences, etc. 

I have had great results with Odyssey (Kismet mono's in the Khartago cases). 

I don't have Martin-logans but have run the Kismets through my various systems that include B&W, KEF. Gallo and Quad ESL speakers, variously and comparatively driven by Levinson monos, Peachtree and Pathos integrateds, Kenwood LO-5 MII monoblocks (total sleepers, still good to this day, also very fast, well damped, etc.). 

The Odysseys are perfectly stable into low impedance loads, very fast (slew rate?), good control (damping without overcontrol), etc., = reliably great sound.

Another benefit of working with Klaus & Co. at Odyssey is that you can pick & choose / customize many aspects as well as upgrade later. 

A good example of which is setting the bias (Class A vs A/B). From the website: 
"All amplifiers: Custom bias for your system prior to purchase. The customer has to provide system information to check feasibility. Free of charge." Nice. Might make sense for your Martin logans. 

It is a smaller family owned business and the ability to speak with the CEO/designer, customize your amps, etc. means that it can take a bit longer than walking into a dealer (support your local dealer, too!) and taking it home that day. Well worth the extra time, "patience is a virtue", at least sometimes.

Lots of great gear out there. Enjoy the hunt... 

Ken

If you can find a better value than an odyssey kismet... I’d be shocked and would love to hear it. Extraordinary sounds at a ordinary price.  And customer service to match any in the industry.