That doesn't tell us much, though. What was the cable you bought and what was it made from? 'Big chunky plugs' might just be eye candy. More seriously, what is this power block you mention and what's feeding that?
Treating your mains means taking a holistic approach to attaining synergy. Replacing a single cable in a possibly non-ideal position in the chain may not achieve anything, as you have indicated.
Don't give up on the whole idea because of one failed experiment. Remember my starting advice - invest in a can of
Deoxit D5 spray and treat every single mains connection in your system. Surely that's worth trying?