If the audio internals are the same as the RCD310, an amp won't do much, but it will help you get better volume output before the head unit distorts. So, you may get more output, but it won't help much with sound quality.
In the end, and amp does one thing, makes the music louder. If your current setup is loud enough, then an amp won't do a whole lot. It has the potential of making the music more dynamic by allowing the high peaks to play without distortion, but if you want a real increase in sound quality, an amp won't make a big difference, you need speakers, a new head unit, and/or a DSP.