Rod,
What you want to do is have something that converts AC from the wall outlet to DC to feed the amps.
Most conventional amps have this built into them. You will need to find out what the amp requires for voltage and current and either buy something off the shelf (unlikely) or build/get something built to do the job.
However, I would think that the amps running completely on batteries will sound better than most power supplies, even good ones.
If the amp runs of 48Volts, you may be able to pick up a used 48V rectifier very inexpensively as that is the telecommunications voltage used to supply DC equipment in the local phone switch, where you get your dialtone. The local switch is usually backed up using 48 volts worth of batteries too. However, the older type of battery is very unfriendly to a domestic environment and may even be dangerous.
What about just using 12V car or motorcycle batteries instead? They must be a lot cheaper than the $560 you quoted and easy to come by. You would want to make sure they are the sealed type and take precautions against leaking too.
I will be very pleased to help in any way I can but I would imagine there are other here with more pertinent advice specifically to do with audio.
