What amp should I buy to power Martin Logan Esl's?

You should replace the peach tree as the power amp for the ML. Job (amazon) makes a nice cheap amp. Use the proper cables on that and you will have a nice system.

read up on what an ESL looks like as a load to a power amp (you'll find that it looks like a massive capacitor). You can read this on Wikipedia & Sanders Sound Labs website. Once you assimilate this info, get an amp that can drive a huge capacitor & not go unstable (i.e. break out into oscillations). Your choices will be limited & will consist of expensive amps (hey, that the physics of an ESL!! don't want to deal with the expense? Don't get an ESL!). Also make sure that you buy low capacitance cables - they don't have to be expensive necessarily but they need to have low capacitance.

Which ML model? Is the bass powered or not?

Bombaywalla, how do tube amps mate with ESL/capacitive loads? I kinda' recall that tube amps "generally" like resistive loads with positive/inductive phase angles. Come to think about it, I'm not so sure that SS amps particularly like super-low impedance loads with large negative phase angles.