Calvinj,
Yes and no that cables matter. The following is what I have found to be true, but that is in my $16,000 mid-fi system.....which I keep upgrading:
(1) XLR cables versus single ended RCA - My system is "true balanced" on the solid state side, and yes XLR cables do sound better than downgrading to single ended RCA
(2) Power supply does matter - Using high quality power receptacles (Furutech GTX-D(G), GTX-D(R), and Oyaide R1 all improved the overall sound. Yes I also have 2 dedicated lines pulled from my power panel, one each for the Panamax power conditioner and one for amplification. Plugging the amplifier directly into the receptacle and not going through the power conditioner provides better dynamics, speed, and soundstage.
(3) As I've upgraded the quality of my components, better cables do improve the overall sound quality....to a point. I use cables that deliver above their price point. Morrow Audio, AntiCables, Supra Cables, DHLabs, Zavfino, Oyaide, Cullen Cables
Cables that I've borrowed above that price point do make subtle improvements, but definitely not in line with the cost of those cables. My assumption is that my system is not resolving enough to hear the improvements that others may hear with higher end gear. Also I don't think my ears are as discerning as some of you, most everything I still own sounds good.....once I got to a certain level of cables.
(4) Cables are system dependent - I have 2 amplifiers, one Tubes4hifi VTA ST-120 tube amp with KT 120 power tubes, and one Denafrips Thallo amp. The best cables for the tube amp are not the best in the Solid State amp, and vice versa
(5) Digital cables do make an audible differences. HDMI I2S (Supra 2.1 and Audioquest Vodka), Digital co-ax (Morrow Audio), and USB (Supra Excalibur, Oyaide, and Wireworld), and Toslink optical (Supra, Audioquest). The most improvement is definitely USB cables, and then Digital co-ax.....I think that just upgrading to use I2S was the biggest improvement; but the Audioquest Vodka 48 8K is a noticeable improvement over the Supra 2.1 HDMI cable....but is 3 times the price
(6) I love to "tube roll" my tube amplifier, and trying and using different cables provides me with similar enjoyment. Not everyone will feel the same