well, i would go 4 direct connect 2 maintain d original quality, but no every HU got those RCA or Aux connector at d back.. n u need 2 make way 4 those wires
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since fm transmitter need u 2 turn d volume quite high 4 both HU n mp3 player, the static noise at d back will be very noticable.. only drawback i guess.. ah, if u bought thouse wireless 1 tat can connect through AAA batteries as a 2nd source of power, it tends 2 eat a lot power, batteries dun last as long as it should..sucks..
the mp3 plug in thngy is ok, but u cannot change the songs order lo, it just play randomly..quality wise is still ok la, consider it play directly frm a thumb drive..