I'm guilty of this. I love most of the music in Spiral knights (mainly because I grew up during the SNES Era, and it reminds me of those days), but there are a few songs I don't particularly care for, the major one being the default boss music.
So I swapped it out for this.
http://www.youtube.com/watch?v=iSONiY5Z7GU
What do you guys think? I think it sounds awesome when fighting Seerus or Vanaduke, but you might not agree.
The fact that you linked anything from Ys makes me instantly love you.