Becker Grand Prix 780

[skitzy.sht]

just got my mercedes as of a week, and i want to put some sound in there
i want to keep the original headunit, which is the Becker Grand Prix 780, and i eventually want to put in sub amp 4 speakers, but just to start off with, im putting in 2 sony 6x9" explod's, now i have no idea about power or anything like this
but i do want my music loud, like drone out traffic noise loud, so im basiically floating in music,

will i need a amplifier, because the radio isnt powerful enough (ill have my zune hooked up to the radio of corse) will it even be good with the amplifier or do i need a head unit,

thanks thats all