Interesting. What single driver are you using? What aspects of performance can to you relate to the speaker and more specifically the greater efficency or design to this improved performance. I've batted this around as well, but have been unable to listen to some of the better representitives of those designs.
I'm currently using a Moth s45 SET with 45 tubes with dynamic Silverline Sonatinas; 93db, simple x-over, flat 8ohm. With the latest upgrade to 24awg solid silver speaker "cables" I'm very satisfied with the results and feel no desire to explore other avenues. That said, I will do so at some point, if only to test the reported results. TIA