[pras870]

Well, with car audio being a specialty of mine, I think I can offer some advice right now. You're not going to be drawing a lot of power, so i'd have to say, the easiest thing to do, would be to buy a simple power supply. Since you're not running an amp, you probably won't exceed anymore then 150 or so watts, so I would use a power supply such as this one (http://www.millionbuy.com/pyrps12k.html). I know it's rated at more then 150, but this is just to be safe. Besides, at that site, the prices only range about $5 an amp above or below. (If that makes no sense, I apoligize, it is 4am here in New York )

And if the deck is rated at 120watts, then that means that each outlet (or speaker connection) is rated at 30watts peak. The RMS power is probably more along the lines of 15-20. The RMS is what you're really concerned about. The peak power is just when say a bass note hits, it jumps to that for a split second (u can also eliminate this if the deck has a high pass filter on it).