Yes, they can make a significant difference. I had some custom made 1950’s 12 ga bi-wire NOS Western Electric cables on my Vandersteen 2CE Sigs, and when I got my Treo’s, a pair of AQ Comets were thrown into the deal. I didn’t initially use them, as I thought my NOS Western Electric were very nice, (and indeed, they are), and I also needed AQ spades for the Comets on the amp side. Finally got some, tried them out, but thinking I could sell them off for a nice profit since they were thrown in with the speakers. Well, hooked them up, and it was one of those ‘wow’ monuments. I knew I could not go back the WE cables. They have been installed since, and are not going anywhere.
Cables, given the overall equipment, can make a big difference, but I think speaker cables can be even more dramatic than interconnects…..overall.