haha brothers always potong ppl and there ppl where got professional wan~ sell all lousy quality product hehh~

PREAMP - its just additional item to tune ur sound more keat

AMP - is to kick ur woofer or mid

4 channel - not play more sound just enable u to kick more device

( e.g. 4 channel can divide into 2 ch each )

lets say u got 2 mid ( focal and pentagon ) u can set 4 channel amp to make it 2 ch kick focal and 2 ch kick pentagon.

and if u using 2 ch ( normally ppl use to kick 1 woofer ) like what i done to my car hehheh~