Advice on wiring Magellan RoadMate 1700 GPS directly into NSX electrical system

I have designed and built my own custom GPS unit to hold a Magellan RoadMate 1700. Its been professionally finished to match the OEM interior and will sit on the dashboard, directly in line with the center console. Its been styled to match general NSX design features and everyone who has seen it so far thought it was an OEM add on. I will post pictures soon, once I get my CCM unit repaired by BrianK (there's a hole in the dash at the moment below where the GPS unit will sit).

I'm looking for advice on how best to wire the unit directly into my ignition system so that it behaves identically to when it is externally plugged into the cigarette lighter. That is, the unit detects power when the ignition is turned on or the engine is started, and then detects power off when the ignition is turned completely off.

Lets assume for now that I can manage to run the wire from the back of the unit and in under the dashboard somehow (that's a question for another day, when I have photos showing where the unit is located). My specific questions regarding the wiring would as follows:

1) Where would I best connect the power cable into the NSX wiring system so that I get the behavior described above?
2) Is there some convenient method of utilizing the existing 12V DC adapter (which is inside the connector that plugs into the cigarette lighter) so that appropriate step down in voltage and step up in ampage is achieved?

If anyone needs more details on the above then let me know.

Thanks - Kevin.

There is a "switched" (powers up with ignition on and powers down with ignition off) accessory terminal in the fusebox above the driver's feet.

Wire into the accessory terminal with a cable that has a cigarette lighter connector on the other end. Then plug the cigarette lighter plug into that to step down the voltage. Be careful to get the polarity correct when wiring into the accessory terminal. Bury the cigarette lighter connectors in the dash behind/below the oem stereo (there is plenty of room back in there).

OR

For a somewhat more elegant solution, you can purchase a hardwired car adapter and tap into the accessory terminal. The adapter steps the voltage down to the correct voltage. Then hide the adapter box somewhere out of sight.

Be sure to get an adapter that matches the voltage requirement of the Magellan 1700 GPS.

Let's discuss installing a Magellan Roadmate 1700 in an NSX and integrating it with the oem stereo system.

You would need a housing - you have already built your own - but word on the street has it that the Magellan Roadmate 1700 is a near-perfect fit in the Honda Display Pod. Also purchase a USA-Spec PA-11 HON and plug that into the back of your oem stereo.

This eliminates your CD changer, but you won't miss it, because you can listen to your iPod/iPhone/iPad on the iPod side of the USA-Spec adapter, and listen to the Magellan GPS directions through the second input of the USA-Spec adapter.

This is not a bad setup for the NSX. If you shop around for components you could purchase everything you need (except iPod/iPhone/iPad) for about $600. For that price, you get excellent (not perfect) integration in a user-friendly complete system that maintains the stock appearance of your interior. You keep your oem stereo system but gain GPS capability, plus mp3 playback, Pandora, or any music service that you can stream on your iPhone.