Acme Audio silver ceramic fuses: http://www.dedicatedaudio.com/inc/sdetail/1895/16482
I put them in my MC30 tube amps and SP-6B tube preamp. The increase in inner detail is freaking amazing. The bass got tighter, and the music came into better focus. TImbre is truer. I'm hearing details I didn't know where in the recordings. And they haven't even broken in yet.
I didn't want to spend $50 for the HiFi Tuning or Furutech fuses, and I'm glad I didn't. Total no-brainer.