With respect, that is nonsense. The Red Wine Signature amp I owned used a small battery within its standard amp-size enclosure and this provided power for several hours of listening. At the end of a session, or if the battery became discharged, the internal power supply could be switched on to recharge the battery or directly supply the amp in the same way most other amp power supplies do.
Batteries cost is nothing like $2000 - why should they? A first-class 12V battery of the Ah capacity needed for a preamp, DAC, streamer, or Class D amp for a few hours' use would be small enough to tuck behind the amp or even within its case if designed to take such a battery.
Yes, and that's precisely why I'm trying to help you. There is no need for fires, explosions or whatever if you have a battery in your audio gear, any more than there is to have a battery in your car. I'm agreeing with you that batteries are in theory a great way of powering your gear, but not if you convert their DC to AC and then back to DC. That would cost a lot and would add nothing comparted with the AC to DC conversion done by a conventional amp with a high quality internal (or even external) power supply. Use your DC to deliver DC straight to the circuit, but only if the amp lends itself to such a conversion.