This depends on the strengths and weaknesses of your amp. The El34's are great in the mids, but a little weak in the bass and rolled on top with my RM9 MKII. The 6550 Svetlana's are great , but they lack the lush mid of the EL34. The 6550 has an iron-fisted bass, better than most SS amps I have heard including some Krells and the like. Buy two sets and trade them when you want a change. Jallen
