What type of cables make the most difference

Back in the mid 90's when I was assembling my 2nd system, the interconnect cables between the preamp and power amp were what I spent most time and money on. Those cables made the most difference in the system.  I ended up with Magnan interconnects after borrowing more than a dozen "revealing" cables.  I could have gone down the same path with speaker cables, but after working with about 1/2 dozen, I quickly ditched silver plated, and ended up with a bi-wired set that went well with my Vandersteens.   As for power cables, created my own shielded power cable for my homebrew preamp.  I tried the same approach on the McCormack power amp with no noticeable difference.  One thing I never got around to was using a similar approach with power and signal lines on the Thorens 125.  I wish I would have.  

Let's ask Paul:

https://www.youtube.com/watch?v=EAuvVCuujkQ

In my experience, speaker cables made the most difference.  I have upgraded my1990s system over the past five years, and I have gone through several sets of speaker cables, a couple of which I had on hand from my previous system. After purchasing a new set of modest but reputable cables, I still felt there was as room for improvement in sound staging and tonal qualities.  I then ordered a set of Fidelium speaker cables—4 ft. cables as I am using monobloc amps.  The improvement was stunning, across the board; even my wife, a non-audiophile music lover, commented on the radical improvement in sound quality.

Beyond that, I found that going from generic USB and Ethernet cables to a modestly-priced but well-known brand cables made an improvement in sound quality, not as dramatic as the Fidelium speaker cables but still significant.

I find this to be highly system dependent.

Interconnects:

I have experienced high-end balanced interconnects making a profound difference in one system and no difference at all in another which I attribute to the design of the gear.

Power cables:

I have experienced power cables making only subtle differences. I think tubes are far more sensitive here but could be wrong.

Digital

I have experienced fairly noticeable differences in digital cables but find USB less sensitive than SPDIF and other formats, though I still use something better than stock. For reference, I previously had Auralic gear which recommended using their proprietary connection (Lightning Link) over HDMI format cable. Upgrading those cables made a very noticeable difference. Lightning Link stock cables outperformed expensive SPDIF, USB, and AES EBU connections. For those who might own Auralic gear - this is an easy recommendation.

Speaker cables

Like most others, here I have found the greatest difference. FWIW - the most profound experience was with my first decent set of speakers where I swapped out the supposedly “high end” low gauge stranded wire and the jumper plate on the back of the speakers with low end analysis plus bi-wire. Shockingly better. From that experience, I took away that guage means far less than pretty much everything else in the design of the speaker wire.

In my current system, all good quality cables sound pretty good but bring different attributes gently to the table. No earth shattering revelations yet though I’ve stopped searching with my current cables because I don’t believe they can be materially bettered.

Quick note to @mike4597 - the Fidelium’s might be the best value in high-end audio. They are truly great speaker cables - period. On a value basis? Off the charts good.

In sum: though I can’t reliably rank in order of importance, my experience is that power cables have been the least important. I’ve never had a holy $hit moment with power cables, unlike for all the others.

As usual, YMMV.

Interesting question and discussion. I was surprised the conventional wisdom was PC. I asked chatGPT for its subjective opinion for MY system … interesting it’s recommendations were much more in line with my investment strategy.
However, it does go on to say… What cannot be verified from primary sources is that “power cables matter more” or “speaker cables matter less.” There is no universally accepted technical evidence establishing such a ranking.