I will agree with you interms of the quality of MP3's, but how they sound on the computer speakers will be identical to that of a home theatre system. Currently with my Z560's im very pleased, yes they pack some bass but I wouldn't go as far as to call them boomy. Im currently looking to either purchase a HTIB/seperate components for Home Theatre/5500. HTIB are simple setups and the RMS is about half of what they advertise on packaging. The only system Ive heard that sounds decent for a HTIB are these 800W Panasonic ones (I get to hear how everything sounds as I work at FS). Seperate Receivers/speakers/subs works out to be much much more expensive than a poor student can afford. We come to rest with the Z-5500 as they use speaker wire and pack 505 W of RMS which would equal an advertised Wattage by HTIB of 1010W. When was the last time you saw a HTIB bundle with anything near those specs at around $400.
The Panasonic ones I heard are going for $549.99 at FS right now (Originally $699.99 earlier in the year). My suggestion is to go to the retail store and bring a CD of your own to test how the unit sounds. Try to have an orginal CD as they sound much clearer as the volume is turned higher up and will give you an accurate read of sound quality.

Hope this helps ^_^