Are you talking about a separate stand alone amplifier or an audio video reciever? I'm guessing the second one is what you are looking for unless you have volume control on the CD player. Stand alone amps rated at lower than 250 Watts can power those speakers but you will want volume control. Any of the major brand AVR's like Onkyo, Yamaha, Marantz ect. will power them as well. The most simple solution would be to pick an AVR that has an input for an mp3 player. I don't hook my mp3 player in due to sound quality issues, but other members may have some good suggestion or solutions.
If you give us more information we should be able to offer better advice. Exactly what components do you have and what kind of budget do you have in mind?