Yes, I do recall that at the time the Spica was revered for its imaging. I could never get past its serious tonal colorations to choose the speaker over an LS3/5a. To me, in that respect the margin is not small at all. I did not (do not) consider the Spica TC50 to be tonally credible, but it is euphonic so I understand why a lot of people like it. Now if one prioritizes imaging over tonality, then there is more of a case, although while I agree the Spica beat the LS3/5a in image expanse and depth, I did not hear it as having the precision and stability of image that the BBC monitor had. Someone else might hear that aspect differently, however.
The impedance issue isn't a current issue, with respect to the consistent poor performance I hear from solid state designs in low impedances. Even a Cyrus doesn't make it, though all other aspects of the sound produced indicate ample current delivery. Current abundance or current started, I consistently hear solid state amps into low impedances take on more grain, less fluidity, less dimension. Sometimes the difference is subtle. But once you get sensitive to it, even small differences argue for the sound at higher impedances. I haven't interpreted this as an issue of current.
In the bass, no question the Spica is more extended. Qualitatively, it still has a euphonic rise, and the transient behavior of the woofer isn't particularly fast. It sounds a little lazy to me, but again is euphonic.
Certainly the LS3/5a, and the KEF drivers it was based on, are dated but no less classic. At the time of their debut, it was as close as you could get to a Quad-like midrange in a dynamic speaker, and it's stiff little box didn't make itself heard like larger models. All things considered, the Spendor update, the S3/5 and S3/5se are superior and work with a wider variety of amps. In the Spica style of emulating small monitor performance in a somewhat larger form factor, the Silverline SR-16 is tonally more accurate and the woofer speed is a better match for the tweeter characteristics, IMO.
The biggest problem with the LS3/5a in a modern context is its poor efficiency and limited power handling. You have to put reasonable limits on the size room you expect them to drive, to avoid frequent sense of compression.
As for LS3/5a bass, it is euphonically manipulated, by design, with its mid-bass hump for illusion. But late in the speaker's tenure in my systems, I learned its bass was better than I believed when I put them on a pair of Osiris 24" sand & lead filled stands. It was the single most dramatic improvement I'd ever made to an LS3/5a system, considerably outstripping the impact of any one change in the signal chain.
Phil
