Here are a few comparisons from my experiences rated from best to worst:
ZCable Live v4
Ensemble Masterflux
Silver Audio Silver Bullet 6.0
Virtual Dynamics Audition
Transparent MusicLink Ultra
MIT MI-330
ZCable Live v4
Ensemble Masterflux
Silver Audio Silver Bullet 6.0
Virtual Dynamics Audition
Transparent MusicLink Ultra
MIT MI-330