Ideal Cheap Low-Watt Amp for Martin Logan Quest

What would be a few ideas for an ideal low wattage dirt-cheap power amp for Martin Logan Quest electrostats?

(Either a power amp or, preferably, an integrated amp.)

OK, so it's a strange question. Electrostats are not the most power efficient speakers. But in my current situation, which is living off grid using solar power, I would like to keep my speakers (ML Quest) and get a small amp. I would like this amp to be dirt cheap and very low wattage. Lets say 50 watts and under.

Suggestions?

Most important factors to consider?

I will keep my current setup (tweaked H/K Citation 16 power and sae pre) for daytime use, but I would really like something for cloudy days and evening/nighttime use. We are on solar power, and at night rely on batteries for power. I love this life, but it does pose a challenge for listening to loudspeakers at night.