ipod vs CD vs satellite

I am setting up a system in a boat with high powered amps and high sensitivity compression horn speakers. I want to use the cleanest possible source. The existing head unit has no built in CD player, but it can control a cd changer, Ipod, or Sirius.
Here is the question..........if I download to the ipod from itunes and use the Ipod adapter that avoids the ipod's preamp, am I getting CD quality from the ipod? I don't know squat about ipods or compression. I do know that I hear a big difference in my truck when I switch from Sirius to CD. Thanks!
Let me rephrase the question. Let's say I download music from itunes directly to the ipod. When I play back that music is it CD quality?

Never mind. I found a website that answered all of my questions.
So, give us a link so we will know too . . .
Just my 2 cents-- My ipod classic, when connected to the back of my jvc truck stereo, sounds considerably better than the cd player. It is connected through the headphone out to analog inputs of the cd player. IMHO
Stpatrick...........here ya go
Apparently the format you use to download makes all the difference.

Dlr..........someone here told me about an adapter that uses the wide flat connector instead of the headphone jack. The other end of the adapter is RCA jacks for your analog inputs. This bypasses the ipod's preamp and makes a noticeable difference.
Baffled- I'll have to look around. Thanks Dan