Lindemann CD - version comparisons

Can anyone post direct experiences about the sonic differences between the Lindemann CD1, 680, and 820 CD players? I am concerned specifically with redbook playback. I own the CD1 and think the sound is fabulous - very musical and emotionally satisfying, if lacking in ultimate detail - just wondering how much improvement in sound I can expect with their later units. I was told by one person that the difference between the CD1 and D680 was not that great on redbook.