Assuming you have it set up properly, if you don't like the sound of an iPod, there is a good chance you are not liking the compression that has likely been applied to the music files in it. Excessive compression of the data degrades the sound. So you need to use higher data files, if this is your only problem.
Now, if you don't like the sound of playing CDs, and, again, assuming you have it set up properly, then you simply do not like your speakers with music and should consider replacing them. An amplifier is not going to change the way your system sounds at normal volumes. If you don't like the sound, get better speakers.