Here's something for you Mega Man audiophiles. Among other updates on Capcom of Japan's Rockman Zero Collection homepage, they now have a sampling of music from the four games on the Collection. And, honestly... they sound better. This is something I suspected they would do a while back. Sure, they're not remixed or arranged, but the quality of the original music does sound better, at least in my comparisons to the Rockman Zero 1~3 original soundtrack, which are presumingly straight from the Gameboy Advance.
See, while I'm no game hardware expert, the music in the Zero series, while good, always had a muffled sound to it, with a bit of steady noise feedback. I figure this is because the audio samples used for the music had to be compressed pretty sternly, lopping off a bit of the high end and saving space, since pre-recorded music and music samples can be fairly big (in fact, for a lot of games today, the majority of their data is simply music and movies). But the DS, being quite a bit more powerful than the Gameboy Advance, doesn't have the same limitations. So while remixing the music would be time consuming and perhaps unnecessary, they could still use the same music but with higher quality samples, and it seems that's the case.
Listen for yourself and see what you think. One thing to keep in mind is that the sound is coming from your computer speakers now, and is not representative of the DS speakers. But I know a number of DS games that have fantastic sounding music, and I'm fairly confident the music in the Zero Collection will be sounding better than it ever has.