What are some good Amplifier choices for Martin logan ESL 15A?

Perreaux 2150B - 340/680/920wpc@8/4/2ohms. I have one on hand for use with difficult speakers like your Martin Logan ESL's. The 2150B can often be found for around $900. 

Really depends on what improvements you’re looking for over what you have now and what sound characteristics are most important to you.  I will say my friend runs his MLs with a Bryston 3B SST2 with great results so maybe something in the SST2 or Cubed series would be worth looking into. 

Check out this thread:

Audiogon Discussion Forum - Amps for ML Montis

Jay starts his audio journey with ML Montis and is looking for the ideal amp for them.

Decware ZMA.  Not enough amp for the bass in such a big speaker but the bass driver is self powered.  I just hooked my ZMA up to a pair of very low sensitivity CLSs and was surprised it drove them well.  It is resolves beautiful midrange and highs.  

I also have a Kinki EX-M1+ which drives them well and is a beautiful ss amp that comes close to tube sound.

Jerry

Sanders Sound Systems Magtech amplifier...

Look for tubes. They work the best with electrostatics.

+1 to ddudeoo3's suggestion of the Sanders Magtech amp.  It is designed with electrostatics in mind and is very powerful.

Solid state Plinius sa100...Tubes Tsakadiris apollon monoblocks tube amps.Krell they match well with ML.

Much more on this subject:

MartinLogan Audio Owners Forum