Please tell me where in the Qur'an or in the ahadeeth that says you have to have beautiful voice to recite the Qur'an?
the hadeeth says "to beautify it" it means to recite it the best one can do. For example: no screaming, no grunting, no speed reading, etc.
After all the Qur'an is the direct speech of Allah SWT, do you not want to beautify when reading it?
"Hadhrat 'Aa'ishah (Radhiyallaho anha) narrates that Rasulullah (Sallallaho alaihe wasallam) once said. "One who is well versed in the Quran will be in the company of those angels who are scribes, noble and righteous; and one who falters in reading the Quran, and has to exert hard for learning, gets double the reward." (Bukhari, Muslim, Abu Daud, Tirmidzi, Nasa’i, Ibn Majah)
More ahadeeth on reciting and listening to the Qur'an: http://www.witness-pioneer.org/vil/h...08/chap180.htm