[motornut]

you may want the amp to get over the road noise
depends on the radio might not have much volume
it's important to find the neg/pos with the speakers
otherwise they get outa phase and would sound low/no volume/bass
if it's not marked you can use a nine volt battery to check for speaker +
note the pos on the battery and tap/touch the wires to the speaker when the speaker pushes out, note wher the the pos side is