When doubling the gauge (cross-sectional area) of copper in my speaker cables recently? Yes. Without doubt.
When investing £25 in the convenience of an Audioquest optical cable (Toslink - 3.5mm mini optical, 0.75m) where every single parameter was just right? No audio differences. None were sought. (I just paid extra to save myself time and to not have to compromise 'ergonomcally' on the wrong length, or use of adaptors, or thick cable, or cable that didn't 'drape' correctly, etc.) Some much cheaper cable (of the the wrong length and appearance and thickness and using an adaptor) would perform just as well i'm sure.
Ex-demo room Chord C-Power 1.5m mains lead for heavily discounted price. Not what I sought originally but is excellent build and shielded. Still overpriced (compared to something from Wilko) despite the 3 x 2mm2 pure copper conductors. Makes a difference? No. Not to the sound. I just have a 'thing' about good plugs and mains leads especially MK and Duraplug etc.
My conclusion (for me and my experiences with my system) is that speaker cables with lots more good quality copper made a difference. All the rest was to keep me happy in other ways than just sound quality.