Cables from amp to preamp or longer speaker cables…

Since you have a lot of Benchmark gear in your system, you may want to check out the Benchmark website and look at their balanced interconnects. They use a Canare starquad cable and charge $144 for a pair of 25-foot cables. You might be able to find more expensive ICs that sound better in your system - but you might not. This could be a good route to go if you're trying not to spend too much money on long ICs.

I have had long runs of interconnects (5 - 7 meters) both balanced and unbalanced for two decades now with really no issues.  Presently, my RCA (unbalanced) interconnects are Audio-Envy and work very well, noise-free and are very articulate, while reasonably priced.  They are low capacitance cables.  The longer your runs, the more capacitance in the cables may have some attenuation in the treble range.  

Disclaimer: I am out of my league when talking headphones. I’m just throwing this out there.

From what I understand, you’re currently connecting your Benchmark DAC 3 HGC to your preamp using the RCA connections. That leaves the balanced outputs on your Benchmark DAC 3 HGC unused.  So, here’s my thought.

Why not set your equipment up in the optimum location using shorter RCA connectors and then buy a headphone amp for your couch area, which would be hooked up via the balanced outputs between your DAC and the headphone amp?

I found a headphone amp on Amazon for $289. Just search under:

S.M.S.L SH-9 Headphone Amplifier THX AAA Technology RCA/XLR Input 6.35MM Balanced Headphone Amplifier

I also found a headphone amp (not on Amazon) for $7,000. So, you have choices.

Try posing this question under the headphone section of the forum. You might get some good suggestions there.

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…ahhh…keep it simple, I’m with erock79

“Get an extension for your headphone cable. That is much more practical than considering lengthening other cables.”

With few exceptions, it is better to use longer interconnects (RCA or balanced) and shorter loudspeaker cables.