Yup definately only one male in a tank.
They aren't called fighting fish for nothing. Which is a shame, because they are beautiful fish. Also with your guppies, be carefull as they are prolific breeders, and you may suddenly find your tank filling up with guppy fry (babies). The males have the stunning tales, so you could maybe just have males? If you do go for pairs, just keep an eye on their breeding as you could fast find your tank running out of room.
Also another friendly pretty fish, is the platy.