I am a true believer that an Aftermarket HU will make the biggest difference in your sound setup.
My girlfriend has a 2001 CR-V with stock sound. The HeadUnit basically only plays cassette and has an FM.AM tuner. So as a gift I got her a Head Unit. It was not one of the expensive one, it was only $200 bucks or so with everything installed and etc. I thought that it was just going to give her the ability to play CD-Rs and there will be no noticeable difference in sound, boy was I wrong.
When we tested the head unit for the first time, we were both in shock. This is coming from an everything stock POS CR-V sound setup to something that sounds as if her speakers were upgraded!! Her bass can now kick and you can feel it in the car unlike before. Sound quality was improved 100% no joke.
Tell your friend that an aftermarket head unit is needed. I am saving up for mine...