i recently bought a used mesa 400 (not the plus) but instead of 6556's the guy was running it with 6 6L6's. i know that this gives the amp less power but i dont have the money to buy the new tubes yet. so is there anything really wrong with running the amp with the less powerful tubes (will it hurt the amp/burn out the tubes), or will it just have less power? oh yeah, and if you have any suggestions where i can buy a good set of 6556's at a good price, i'd appreciate it. thanks for your help.