i would use a power supply.....30 amps and up...depending how much amps your amplifier/head unit...ect.... requires....(radio shack sells power supplies)......
Yes they do but generally most stores, due to fairly low demand and more competitive pricing from other manufacturers, do not keep the higher amperage models in stock. Consequently more often than not if you're looking for a Realistic power supply any bigger than 8 or 10 amperes it has to be ordered from RadioShack.com or through your local store ~ but either way you're gonna wait.
The Pyramid Phase III power supplies are solid units (the only Pyramid product I would ever own personally) and generally cheaper than their Realistic competitors. If you have a CB and/or ham radio equipment dealer in your area they will most likely keep these in stock. Well, either Pyramid or Astron units...