AT analog output

Recently, I plugged my CD player back in and actually played a good old
fashioned original CD. I was suprised how good the CD sounded after many
months of only playing music through the AT. So, I tried a little
experiement comparing the same track ripped differently against the CD
played through the CD player. Now keep in mind, my CD player is nothing
special. It's a rather old Denon 5 disc changer using analog outs.

First, I compared the track ripped at 128 kb/s using MusicMatch against the
CD. Well, I don't have to tell you what a joke that was.

I then compared again with the same track ripped at 320 kb/s using EAC/LAME
preset insane. The difference was noticeable, but the CD still sounded
significantly better.

Finally I compared the WAV ripped using EAC. I thought that the WAV at least
had to be at least close to the CD in quality, but it was barely any better
than the 320 CBR mp3.

Now, I am using the analog outputs on the AT, so I had to adjust the volume
when comparing, but there was also a very big difference in the depth of the
sound especially in the base. Even the WAV had much less base than the CD.
So, here are my questions: Is the analog output on the AT SO BAD to explain
such a difference? Is there any way to improve the quality of the analog
outs without opening up the box? Should the quality of a WAV played through
the AT digital out be at least as good as a CD played through a decent
consumer grade CD player with analog outputs?? I just would like to know
what kind of difference I should expect before blowing $$  on a new receiver
with optical inputs.

Thanks for your input.

Jeff