High-Efficiency Single Driver Speaker System

For those of you who have gone to the 'Dark-side'---a high-efficiency single driver system and never looked back, I'd like to get your feedback on two specific things: 1)What type of music do you mostly listen to, and 2)What do you find are the most appealing characteristics that you find lacking in more traditional lower efficient, high power amplifier-based system. I currently have a custom EL34 JWN customized amp rated around 35-45 watts and I'm thinking about going this route.