James et. al.,
The circuit shown is a fine and simple power supply but...
The output is unregulated so the voltage does vary quite a bit with load changes and with line voltage. (audio produces some wild load changes.) There is no provision for limiting current when charging the battery. A dead battery will take as much current as can be pulled from the transformer. For a fixed current transformer, adding output capacitors will likely draw the output voltage down below 12 volts. There is no protection fuse shown. Be sure to protect the circuit by fusing the input to the transformer. And one thing that hasn't been said yet, a 25 amp transformer weighs a lot!
I still like one of these for your application...
http://www.radioshack.com/product.as...ct%5Fid=22-506
http://www.radioshack.com/product.as...ct%5Fid=22-504
or if you need 25 amps...
http://www.radioshack.com/product.as...ct%5Fid=22-504