HD Radio
 

I have a 2006 X5 4.4i with DSP and 6 cd changer Nav radio.

Is that HD Radio? If not, how can i get HD radio with a better sound quality.
I just rode in my buddies 2008 325xi and the basic radio sounds so much amazing in his car.

thanks for any input,

You are correct your current radio is not hd.
I went with an aftermarket solution to get hd.
Directed "Car Connect" Universal HD Radio™ tuner Add HD Radio reception to any factory or aftermarket radio at Crutchfield.com
or this one Sears: Online department store featuring appliances, tools, fitness equipment and more same remote different name. I had them both sold one with old car.
I connected it to the aux 3 input with my RSE. Its also used by my rear passangers for rear seat radio when Im using another source. I can get you a pic if you want.