> I wonder at what point we can spot the SMBHs/supernovae that had given rise to our own solar system

Likely never, if you mean an actual supernova remnant that released the enriched material into the interstellar medium. Partly because the formation of the Solar System requires that the enriched material mixes with the ambient gas and cools. That means the supernova remnant would most probably not be identifiable as a distinct entity. The other reason is that there almost certainly isn't a single supernovae that gave rise to the enriched material that formed the Sun and Solar System. The enrichment probably happened through multiple generations of star formation and supernova enrichment cycles.