Where did the extra amps come from? Did you have another +12V rail you didn't know about? Or, are you referring to "Peak Amps"? Now that I think of it, you should have 41 combined amps since you do have a 500w PSU. That being said, you should have three +12V@18A rails. I should've asked you before, but does it say exactly how many amps the +12V rails supply? (it's usually right under where it lists the 12V rails.) But to answer your question, yes. If you have a multi rail PSU that can supply the +12V rails with a combined 32 amps of "Continuous Amps" that should be enough to power the 380. Just as long as you don't game for longer than 8 hours a day. But if you actually have 41A that would be better for extended use.
I should also state that calculating combined amps on multi rails isn't an exact science. There are a lot of variables, like the quality of the metals used to make the rails, and also how thick the rails are. Just so you know; basically, Rails are just thin narrow strips of conductive material on a PCB (printed circuit board) that carry electrical current from the AC/DC converter to the cables that plug into your motherboard, graphics card, etc... The main reason for rails is so that the current coming from the converter can be accurately monitored and maintained. This is why a lot of people are right in believing that multi rail PSU's are safer. The reason is because they are limited at lower currents, where as a single rail isn't. So if you don't have a good single rail with OCP (over current protection) you run the risk of blowing all the components connected to it. A good multi rail should still have OCP, but at the lower currents there isn't as much risk versus a single rail. Sorry for the long winded explanation.