Suggestion on XLR Cables

In my very limited experience with short runs and fully balanced gear (Ayre), I have found balanced ICs to be less variable in sound quality than single ended, which intuitively and technically makes sense. Eg many people report Mogami Gold to get them most of what they need sound wise. I would start there before spending a ton of money, then audition a few things to see if it's worthwhile.

My personal go-to for both RCA and XLR is DH Labs Air Matrix, which runs in the $300-400 price range brand new. It's quite neutral and detailed and won't add a ton of its own color. In XLR I have found it to be very close to ICs costing 5x as much.

If you need something on the slightly sweeter side of neutral, Audience also makes very nice stuff. And of course there is Cardas but I have found their stuff to be very system dependent.

Ah I see you already have Dueland XLRs. Anything in particular you’re looking for that they’re not giving you? On the higher end side, Audience Au24 SX is fantastic and could be a great match for your system, but likely out of your price range even used.

...What are those mid to high end cables (RCA or XLR) made out of to warrant such premium prices (few hundred dollars per cable)?...

I think snake oil is a key ingredient.

I agree with marcyun that so far I've heard very little difference in XLR Cables unlike RCA's where there are significant differences. As mentioned for little money the Canare are good. For a bit more the Solid Silver or Silver Litz XLR's from Sunny Audio Shop on E-Bay allow a bit more micro, macro dynamics through.

There are a pair of Audioquest Diamond XLRs on auction on Ebay now. I prefer any of Synergistic Research top cables the Apex, CTS. With the time of year now is the buying and selling time. Most any of the better known cable companies that have more time in the field of cables have also spent more R&D time, and will get you the results you are looking for.