I strongly agree about Avante Garde Duos and SET. The horn colorations are obvious but they have magic in their musical presentation. They do not have any better dynamics than a regular cone speaker. Based on my listening I think this is a myth. Yes, they can play loud but their dynamic range = difference between loud and soft is no different than, say, B&W or Opera speakers. You'd need Quad ESL's for better micro dynamics but they don't play loud like the Avante-Garde's.
Staying on the "audiophile" track I liked ATC active 100's which have very dynamic bass and can play 115dB all day.
But if it was me, I'd go with a good full range single driver speaker with no whizzer like Bob Brines Fostex FT-200 speaker. You can't get high SPL and good sound for the most part. Also most speakers that play loud can't play soft. It's either one or the other.
If you ever lived with a good single driver speaker you be surprised:
* time and phase coherent.
* sound from point source.
* No change in voicing as with multiple drivers of different materials.
* Excellent PRAT.
* No crossover to add distortion, coloration, absorbs power and the dynamic range of music. As Bobby Palkovic at Merlin said, even adding one capacitor to the x-over creates audible nasty sound.
So the first thing you notice is no bass, no loud volume level, lack of detail, especialy in the HF. Wow, you say, this speaker sucks. But live with it for a while and you get over the audiophile traps and realize real musical satisfaction does not come from these things. My experience anyhow.
