When does a PC makes sense? Is there a special case/circumstance?
When equipment is designed defectively (ie by cost controls).
Anything a Furman does must already be done better inside electronic power supplies. Does not matter how 'clean' that AC power is. A power supply first converts power to high voltage radio wave spikes. And then 'cleans' that much 'diriter' power. The 'cleanest' power from the best conditioner is first converted to 'dirtiest' power before superior 'conditioning' circuits inside electronics 'clean' power better.
Power conditioning is most for equipment with inferior power supplies. Supplies that are missing essential functions. Is often touted by hearsay to do things even the manufacturers does not claim.
Some power conditioners do more. Others sell at a same price to do less. The only place they cannot lie is in the manufacture numeric specifications. Any honest answer always references those numbers. Less reliable recommendations hype brand names rather than spec numbers.
Most failures are due to manufacturing defects. Defects that can result in failure months or years later. Many then only blame what advertising hypes - 'dirty' power. Power rarely cause hardware damage. Few learn why failures occur. A power conditioner solves little. Typically only does what is already inside the power supply - or less. And sells at extreme profits.
If a power conditioner does something useful, then the recommendation defines each anomaly with numbers. Then says how that power conditioner averts hardware damage from that anomaly. A short list of anomalies to solve: frequency variation, power factor, noise, EMC/EMI, harmonics, floating neutral, voltage variation, current leakage, floating ground, sags, or blackouts. A power conditioner recommendation says, with numbers, why each is harmful. And then cites the power conditioner spec number that claims a solutoin.
Good luck. Many who recommend power conditioners do not even know what those anomalies are. Just know from advertising that power must be 'cleaned'. Useful answers cite manufacturer spec numbers for each anomaly.