Ok, the wires I used are on the back of the deck, and are as follows:
Battery POS - Pin 10 on the 20 pin plug (Red / White)
Battery NEG - Pin 20 on the 20 pin plug (Black)
Accessory - Pin 1 on the 20 pin plug (Yellow)
Dimmer - Pin 9 on the 20 pin plug (Green / White)
Antenna Pow - Pin 14 on the 20 pin plug (Pink)
As PDX shown above. You said you wanted ignition turn on.
you would only want to tap into the Accessory pin.
Battery+ will have you gauges lit all the time.
Dimmer if only if you gauges has a dimmer wire
Antenna, or remote turn on line are fairly weak, most range from 0.5 amp to 5 amp
I would not use them as a power source unless you have a relay wired up to some
power from the battery. When you start using relay then thing starts to get confusing.
Best bet would still use the Cig-lighter, or Accessory - Pin 1 on the 20 pin plug (Yellow)