re polishing: i recently did it in stages.

bear in mind all my amps, pre and two monos are 6 years+ and never cleaned to my knowledge.

i polished all my plug pins 5x plugs amps_ cd + 6 way distribtuion block.

change noticed: maybe  a tiny perceptable increase in clarity.

i then did all the plug fuses and internal fuses, 5 x plugs and 2 x internal fuses.

change: an obvious increase in clarity.

i then did all my rca plugs and connectors: bear in mind all my rcas are solid silver plugs.

change: none zip nada absolutely nothing..

so in my system and to my ears there were small gains to be made wholesale over the entire process, but in scale of effect they were no more in total than changing my cd-pre IC from crap copper to 5n silver+ silver plugs.

to put this in perspective,changing the house supply inlet fuse to 100amp and using a dual busbar for the mains wrought an improvement as siginificant as my last amp upgrade, which was pre and integrated to better-pre and monos.

however the most significant change i've yet had from a single upgrade was adding a silver power cord onto my old integrated, back in the day before i had the pre-amp. that was absolutely night and day...

so it's fair to say these things are hugely system dependant