Do speaker cables really make a difference ?

For me speaker cables made a difference. And if you’re curious I encourage you to experiment. Then you can be the judge. 

Yes, in my case cables used anywhere in the system have an effect on sound. Including speaker wirings and even the electronic PCB cards tracks have an effect. I had an old tube preamplifier I disconnected all the PCB tracks and replaced them with point to point wirings. The sound improved a lot.

If you want to test try these tow cheap cables below recommended by Whathifi. Try them separately first and then both connected in parallel (Make sure the cables get enough burn in time first). The Clearwater is good with treble while the Rocket is good with bass. I use them connected in parallel.

Van den Hul The Clearwater and AudioQuest Rocket 11

Even the wires in the crossover coils have an effect. I replaced the LF filter coils with Jantzen Audio WaxCoil 12awg and the sound got better. I will replace the rest soon, I had already replaced the capacitors some time ago.

Post script: 

I got some anticables many years ago and they sound fine.

As previously remarked: at some point accept happiness in how your system performs.

Unless you have access to exotic conductors, the 'amount of metal' (i.e. gauge) of the cable/wire is the best measure. That having been said, if decent gauge lamp cord isn't good enough for you, paralleling 2 or 3 strands ought to do the trick. Thank you Dr. Ohm. If you are concerned with increasing capacitance(?), a cable containing the same amount of metal as the 3 lamp cords would have the same capacitance issue. Electric current is remarkably disinterested in other details except for loops in the wiring and oxidized connectors.

The confirmation bias story I like best:

A man was walking in Manhattan with a bag of salt slung over one shoulder.  Every few yards he took a pinch and threw it over his left shoulder.  Someone came up to him and asked him why he was doing it.

'Keeps the elephants away.'

'But there aren't any elephants for miles around here.'

'Effective, isn't it.'