One thing to keep in mind while using a 12v power supply is the amperage rating of the supply is very important to take into consideration. A '20 amp' supply is not actually putting out a constant 20 amps. Which matters greatly. Consider using a power supply that is actually rated at 30 or 40 amps to see a consistent 20 amp duty rating. You'll never starve the radio and you won't over work your power supply.