RCA interconnect recommendation

Cables are the worst bang for buck in the system. If you feel the need to spend much more money, you would do much better to upgrade a component.

That said, cables do sound subtley different. Since you already have cabling that works, I suggest that you try before you buy. Make every new cable prove itself. If the difference isn’t clearly audible, then put the money into a fund for a component upgrade.

Or, DIY. You can get perfectly acceptable RCA connectors made by Switchcarft from Digikey for $5 or so, which are reasonably close to WBT or ETI at several times the price. You can also buy very good cabling from Mogami or Canare, professional microphone cable, for $1 a foot. The sheilding on both of these is excellent, and is necessary if you live in a microwave-rich environment.

The only exotics I use are cartrdige-to-phono. The rest are Canare Starquad microphone cable with ETI RCA’s, which serves an ESL system with a higher end Koetsu as source.

IMO. YMMV.

Take a look at Hapa cables. I bought a Breathe Copper and a Quiescence Copper with the upgraded connectors for my system which is quite frugal compared to most here, but holy crap did it make a huge difference in clarity without any harshness. On paper it would seem a waste of money but hearing the difference first hand it is amazing the difference, and it's an upgrade that will last. Well worth a look.

You can’t go far wrong with chord cables. I’d entertain both the C-line and the Clearway...both are quality cables and are lower to mid tier amongst their offerings. Both have received numerous positive reviews and even won awards. I’ve been using them for years to good effect. I don’t think they add or subtract anything, they just seem to go about the business of transferring the signal as presented.

QED, as well as Atlas make some terrific similarily relatively inexpensive cables. QED’s reference, and Atlas’ element integra....Ecosse makes the conductor and the composer line of cables that are very good as well. I currently use all of the above cables in my system. Notice, most if not all the cables are UK products. I’m a bit partial to both equipment and cables made there. My system is about 80% made in the UK (Actually made there!), short of my Border Patrol dac and my Marantz Reference stuff.

OP.   "It's a curious problem of "you don't know until you know" sort of thing.""
 

This is so true! But also one of the things truly wonderful about high end audio... there is virtually no end to it... the more effort you put into it the better it sounds. A pursuit of constant discovery.

It's a curious problem of "you don't know until you know" sort of thing.

Yeah, except you haven’t shared what improvements/sound characteristics are most important to you.  This is exactly how we can help you achieve your goals, but if you don’t share what you’re looking for the recommendations will just be all over the map.