Have problems running a 8 ohm, 89 db speaker

I bought a minisystem from overseas, those that have a 6 ohm amp, that is supposed to be able to drive things that are more efficient than the speakers provided 81db efficiency, 6 ohm two way vinyl clad speakers. Well, I have this minisystem as a source system, has 3 CD charger and a MD recorder, with its power source being a 220volt to 110 volt transformer. I tried to run the EPOS ES 11 from its amp section and the only thing I get is very bad quality sound. I remember this system really pounding the 6 ohm, 81db it had come with, and now, I am wondering. Does this driving issue have to do with the fact that the amp section of this minisystem, which is rated 25 watts at 6 ohm, can't produce enough watts to drive something about that impedance? I always notice that amps produce more watts as they go down while their wattage goes down as impedence goes up. What do you think is the problem with this set up?