My experience running long (8M) balanced pre-power interconnects is that there absolutely is a difference and frankly the longer lengths only exacerbate it. I clearly heard improvements going from Nordost Tyr to AQ Sky to AQ WEL. The only problem of course is the cost of these very long runs. One thing to bear in mind if you are purchasing a long run is what after sales service the manufacturer offers. When I moved I no longer needed a 10M run so AQ were happy to re-terminate my 10M WEL cable as one 7.5M cable and two 1.25M cables at a very modest cost. As the market for very long runs is probably thin having this manufacturer supported flexibility is very valuable, I'd recommend you check if Acoustic Zen can do this for you should you find your needs change in the future.
