The Z-5500s aren't that bad, especially if you listen through foobar2000 with wasapi output (google it for more info). I have a pretty good headphone setup, so I think I know good audio, and the Z-5500s are great for the price point.
On that note, they are $250 at amazon, free shipping. Not a...
Something else to try: I just spent some time with a vacuum and a can of air cleaning my Antec 900, it is much, much quieter now. I think something got stuck in a fan causing it to rattle for the last few years.
with foobar 2000 file management you can copy your entire library to a specified folder with whatever paths you want. you have to check file management when you install foobar2000 as it doesn't install automatically though, so you may have to reinstall foobar2000.