Ok, time I waded in here. As far as I can tell, cables make a difference.
I've tried four different types of speaker cable that I had lying around, as I wanted a certain sound but couldn't at the time afford the "correct" cable for my system (Naim).
I started off with QED 79 Strand. Reasonable and neutral, but lacking in excitement.
Secondly was Gale 315 strand. Definitely more bass, but lost the top end a bit.
Thirdly was Maplin "High Quality" speaker cable. £13 for 20m!. Least said the better, but come on - 65p a metre, what was I really expecting...probably a worthwhile upgrade for micro systems though.
Finally, I tried some Fisual Pearl 2.5mm. £1.60 a metre, and I can say confidently that it gives the sound I'm after - open with tight bass and a clear top end, without being too sharp. Now, it might not be as "good" as Naim A5, or as fast as a Nordost, but it works for me, and at 1/10th the price!
So yes - from my experience, speaker cables at least, make a difference. A worthwhile one at that.