Carl,
I was going to suggest both the battery and the ralphmasphere route. However, almost by definition, there is nothing which is going to make Class A amps efficient enough to be eco-friendly. Running Class A monoblocks to drive Magneplanars is equivalent to running a pair of large hairdryers (or electric clothes dryers) all the time - i.e. a SERIOUS power suck. The easiest way to be 'ecologically friendly' with Class A amps is to get super efficient speakers - probably horn-loaded in some way.
Solar's cost/kWh sweetspot (in terms of capacity or goals) changes all the time, and in the northeast (making an assumption here), solar is a tough way to live sometimes. I am convinced that if you are in the northeast and you want a decent-sized house, the ideal is to build with some active solar, a fair bit of passive solar, lots of insulation, and lots of geothermal; and if you are aggressive, count on being 'net zero' rather than 'completely off-grid.' Why more people don't use geothermal for heating/cooling is beyond me. It pays for itself very quickly (as do passive solar design, insulation, and argon-filled windows, etc), especially if building from scratch in a place where you can dig deep cheaply. thinking about it on an after-tax basis, it makes even more sense. If you live in an area where hotsprings can be drilled to without a huge cost, the whole equation changes because depending on temperature and flow, you can generate electricity from that more easily (though if you do tap hotsprings, I urge you to recycle the waste water back into the system - hotsprings do 'dry up' if not replenished).
