Fbhifi - I'm currently evaluating EG Fat Boy's and Cobra Powersnakes on my tube monoblock amps. There are obvious differences. If your system tends to be overly rich or weighty without the EG Fat Boys, I'd lean toward the Powersnakes. However, the palpability, especially of vocalists, is better with the Fat Boys. The Cobras provide a slightly taller and wider soundstage, with excellent separation of instruments and timbral accuracy. My experience with ARC tube amps would suggest that the EG Fat Boys would be the best choice as long as you're using Powersnakes on the front end equipment. Just my $.02.