Don't sell short the source, if your source unit don't retrieve the detail off the disc nothing you will do downstream will allow you to hear that detail because it isn't there. So the best speaker in the world is just wasted because you aren't sending it anything, garbage in, garbage out.

If your source is only a 80's CD player then your first upgrade should be a CD player. Digital playback has grown astronomically since then. An entry level Cambridge or Marantz would open your ears compared to what you have and those players aren't hard to beat.