Well, that's not always true - there are different releases and masterings, so it depends. I don't know which album you're talking about but for reference this is the dynamic range of Melody Gardot album The Absence in 24/96
http://www.dr.loudness-war.info/details.php?id=33074 and this is the same album in a lossy rip from a CD
http://www.dr.loudness-war.info/details.php?id=28981 - the lossy rip clearly has superior dynamic range and will sound better even though it is in lossy format.
Edit: Actually, I just saw that that's the album you're talking about (sorry, I haven't slept for the past 30 hours). It's a well-known fact that sometimes certain CD releases are better (or on par with) the HDtracks ones even if they have lower resolution and sample rate. That's not HDtracks fault completely coz they just sell what the music studios provide them but a lot of times it's not great at all and people pay extra just for the gimmick that it's hi-res while in fact the dynamics are crushed and the sound is worse. Of course, there are a lot of great quality albums on HDtracks but I've learned my lesson and check all releases before shelling any dough for nothing. That should be your best friend in such situations
http://www.dr.loudness-war.info/ . of course, aside from sites like hdtracks there are a lot of vinyl rips with high resolution and excellent dynamic range that will be great for a DAP that supports it.
So in this case you're right - the CD sounds better but that doesn't make the x3's hi-res support a gimmick - with the right album from HDtracks it will sound better.