Thank you for the posting link.
Another question I have is about the amplifier. Can I use this http://www.kingrex.co.uk/leadacid_battery.html instead of the wall wart with the SRM-252S?
You can, but you should use an intelligent Lithium battery pack.
The battery should should cut off power before it gets too low, to protect the battery from over-discharging, protect the battery from getting too low..