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 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 amp rated around 35-45 watts and I'm considering going this route after having been in the more traditional camp for over twenty years. Thanks in advance for your feedback.