While no one or two (or N) metrics tell the whole story, I learned that impulse response and (and cumulative spectral decay) are among the useful measurements. When I saw those of the Sierra 2 and Sierra Tower with RAAL, both of which I ended up buying, it was absolutely in a different class than everything else I had seen. It's like other nice speakers were sports cars and the RAAL was a space shuttle. Even the highest-end speakers can't campare (to these measurements, not necessarily in overall performance). Compare with measurements for the Magico Q7 MKII and Focal's Grand Utopia BE, then compare price. It's a fun exercise.