Most separates need a larger input power than your stock stereo can handle - meaning an amplifier is almost always needed (AFAIK). Meron ako nung Targa seps, nung hinihintay ko pa yung amplifier ko eh dinerekta ko muna sa head unit, gumagana naman kaso sobrang hina. Nung ni-wire ko na sa amplifier dun na gumanda at lumakas yung tunog nya.

So probably your separates are not receiving enough power. Either balik ka sa stock speakers or bili ka amplifier. Suggest ko amp route para in case you want to upgrade madali na lang.

Not really an audio guru pero dumaan kasi ako dito