The only one that might be worth the $20 is the Les Paul one. In addition to being a great guitarist he is a great innovator and even an inventor. He invented the solid body electric guitar, thus greatly reducing the problem of feedback on stage. He also invented the idea of over-dubbing allowing one musician to record many parts for a single work. Not to mention his innovation of synchronizing a number of recording machines to allow for multi-track recording, thus making mixing after the performance possible. Modern recordings simply couldn't exist without his vision.