There should be a significant difference between the Technics and the Havana. It's possible your system isn't resolving enough or your ears aren't trained to hear the difference. I really doubt a power cord will change much.
I was in a similar situation years ago when I compared a $50 Sony CD player with a Rega Planet 2000. I couldn't detect a difference after weeks of comparison. It wasn't until I upgraded the rest of my system that I eventually heard an improvement.
You might want to consider some other gear changes. I don't know anything about B&K equipment, but your Paradigm should be fairly revealing speakers.
I was in a similar situation years ago when I compared a $50 Sony CD player with a Rega Planet 2000. I couldn't detect a difference after weeks of comparison. It wasn't until I upgraded the rest of my system that I eventually heard an improvement.
You might want to consider some other gear changes. I don't know anything about B&K equipment, but your Paradigm should be fairly revealing speakers.