What I'd like to see is a method that can capture and present dynamic / transient behavior differences of amps - namely in amount of feedback. Feedback does wonderful things like tighten up the bass and extend FR, but it closes the soundstage and makes everything flatter and duller sounding.

I think that breaking the FB loop and looking at open-loop behavior would be very insightful when attempting to correlate amplifier performance to perceived SQ. I know that Jason has said that part of his design process includes carefully examining and optimizing open-loop performance. There's no doubt in my mind that that's a critical step for any analog design engineer.

If we operate on the premise that the transistors/tubes/components can add/subtract certain qualities based on their "intrinsic" sound, then it makes sense to try to examine the given device in all facets of its operation. It's worth asking exactly how linear a BJT is before you wrap it up in feedback. Same with a triode or a MOSFET. For amps that rely upon their global NFB loop to stay stable then forget about it...and same with opamps since they can have +100dB worth of open-loop gain. But interesting to think about nonetheless and something I'd like to examine myself.