My tuppence worth...
I tried a Tacima. With hi-fi, I noticed slightly improved separation with a smidge' of tighter bass. With AV, it made no difference to pic quality or sound.
Couple of months ago I tried a Wilkinson/MasterPlug mains block. Yes, the sound was clearer and more open, but somehow it sounded 'smaller' overall compared to the Tacima's richer, fuller 'concert hall' presentation. The Tacima remained.
However, at the time I was unhappy with my Chord Co Carnival Silver Bi-wire speaker cable - IMO it sounded unbalanced.
So, I tried some Rick @ Musicraft-recommended 'generic' 6mm, 100% copper (oxygen-free) cable, which, IIRC, cost less than £5/m. After setup, I tried my system and, yes, it now sounded very balanced but also a tad 'gloopy' overall.
Then I swapped the Tacima for the MasterPlug, which gave me my 'concert hall' sound but with a much clearer, sweeter and open presentation. Adios, Tacima.
FWIW, my brother is also a MasterPlug convert - and his system feeds off London leccy, while mine uses Somerset's.
By the way, Sainsbury's currently has a special offer on the 10-socket MasterPlug surge protector: reduced from c. £19 to £11. Worth a punt, eh?