Hi folks,
I want to reply to Oles last suggestion as seen in the above post:
The test was done at my friends apartment, we used his HP notebook, Windows XP, Sonata Music server (iRiver) & his highly modded Monica with a brilliant modded AKG Headphone. I may also add that later I verified this exactly within my high end home system.
1. We used a FLAC file: Patricia Barbera "And beat goes on"
2. We converted the Flac to Wave with DbPowerAmp and later changed to flac and son on...
Goal was to verify if sound changes can be detected during these convertations.
My friend and me discussed our listening findings and both shared (suprisingly) the same result.
I don't want to go as far to "objectivly" say we detected "improvements" but very definitve differences!!!
Speaking subjectivly its no question we gained enhanced SQ by different format with a winner called WAVE.
Details:
We started by Particia Barberas Flac I had on my HDD since years. Its a 44,1KHz-16bit file from a CD.
Music: In the first seconds the live atmosphere openes up and the crowed can be heard talking, moving chairs... the room acustic can be identified easily = we have a small club were Patrica playes. The bass player openes up ...followed by several hand claps in rythm. The claps have a nice stereo effect. Later Particia sings and she plays hammond organ with sweet harmonics.
We converted the original FLAC to Wave by the program
DBPowerAmP and listenen again:
For us two we confirmed about the new produces WAVE file that the stage, the air gained a lot, In our ears the noise floor was improved. Especially the first seconds of club enviroment before the "beat goes on" was much more detectable!!!! Felt like the Flac did cut this away = the "air" inbetween wasn't important. With Wave the swinging claps were more lively - the whole scene was playing more authentically.
OKAY we converted the WAVE back to FLAC:
This FLAC was now slighty better than the original FLAC but not as good as the wave.
That is a very strange expirience no one had thought about

But definetly this flac sounded different than its original. For us its the better flac now

And once more. The 2nd FLAC back to WAVE again.
Again the improvements are back.BUT!!! This 2nd WAVE isn't as good as the first converted one. Somehow logical - but still these effects were shocking us

We made this until the 5th conversion and noticed a minor degradation growing each process.
OK but we didin't really started a science here. I'm sure there are things to discover - buts not our task.
what can my friend and me conlude after this night? Well with a windows system you'll expirience differents in uncompressed formats. For us the WAVE is the winner. It has less noise floor. Its produces a different staging image
(Really). WAVE is at the musicians side. You'll get a natural impression that humans play instruments in front of you. With FLAC we had a rather "overall" sound presentation. Details or the "close up" view were not as present- at least influenced by the feeling of less darker background.We're just catching the first thing of an investigations ==>
the effects. What factors may be the root cause? I don't know??

Ole probably you can interpret this findings better than me... I'm interested in what's your opinion.
For all the windows user it may be helpful to try this conversion as well and probably gain some sound quality without investing money. If you're able to confirm it - I would be interested to read it here.
Thanks Jochen