[poker]

I was in the mobile audio industry for a few years a long time ago, and although the components are much better today then they were back then one thing remains constant: The output will only be as good as the input. Meaning: clean signal in= clean signal out.
Your components sound fine and yes an amp to drive the subs will be needed, but depending on your budget, I would also entertain the thought of a new head unit and/or multichannel amp.

Also keep in mind that many aftermarket speakers are 4 ohm and many factory speakers are not which could affect actual output quality.