Some of the variables you have control over:
1) file type. MP3, WMA, etc.
2) bit rate - I've had good luck with variable bit rate MP3's - they make the best use of space IMO.
3) ripping software. If you're ripping your files from CD's, the software you use to rip them can make a big difference. I use LAME, and a GUI interface to LAME called Exact Audio Copy.
4) headphones. Alot of time, with these players, the headphones are the cheapest component. Investing in a decent set of earplugs/headphones might help.
5) firmware - sometimes things have been corrected by the manufacturer, and you can get the latest greatest version from them and install it on your player. Check the manufacturer website.
6) Finally, sometimes the problem is that the player just produces lousy music. I can't say whether this is the case with your Siren, though. Good luck to you!
Wendy, February 2006