when i turn up the volume the music doesnt sound so clear..there is some static..is the problem with the speakers..i have a stock audio system..Ive been thinking about upgrading the casette receiver and speakers..My main thing is that the music is clear and loud..and a really nice bass

 

Probably a combination of the two, your headunit is probably distorting a little bit and your speakers are most likely starting to bottom out.

Depending on your requirement for loud music (we all have different tastes) that could still occur with an aftermarket deck and new speakers. Chances are though the replacement speakers will have some more power handling capability so that they don't begin to bottom out on bass.

The headunit can still distort though above 2/3 - 3/4 volume. The reason is that despite those high power rating on aftermarket headunits (besides the Pioneer and Panasonic Mosfet decks) most actually deilver around 10-15 clean watts of music power as one would compare in a separate amplifier. The decks with Mosfet chipsets can feed about 20-25Wrms cleanly.