Yes those Chesky files from HD Tracks are amazing sounding. If you go to HD Tracks and register and then download the HD Tracks manager, you can get a very nice free sampler of similar but different tracks, some of the artists are the same. Also if you are a member of AudiogoN , they offer for five dollars, an HD Tracks Chesky Binaural sampler. There may be a couple of tracks that are the same as the supplied sampler that comes pre-loaded on the X3, but the bulk of the tracks are different and again mostly the same artists from the Chesky fold, and of course there is the 15% off coupon for HD Tracks that comes with the X3.
The only thing concerning the Binaural sampler that comes pre-loaded on the X3 is that it seems to take up almost half of the available internal space of the X3, which considering they are FLAC files doesn't seem to make much sense. When I first powered up my X3 and checked the available internal space it was only just over 4GB. I understand the software and firmware will take up a little room but all of that and the Chesky files in FLAC shouldn't take up almost 4 gigs I wouldn't think. I'm not sure how much of that 4GB you would recover just by deleting the included Chesky sampler.