One comment - if you're currently using an SMPS to power the TAP-X, then using a cleaner power source avoids dumping noise onto the power lines that may impact other components in the system, even if the TAP-X itself is immune. This could just as easily be a decent but inexpensive linear power supply, however - you don't necessarily need a battery. And even that may be unneeded if your power conditioning is up to the task.
(My TAP-X is powered via a Pi Audio Battery BUSS, but I already had it to power other components in my system, and it was cheaper to get a new B-BUSS DC umbilical to feed the TAP-X than to get another linear power supply.)