Please, what's the difference between 4 and 8 core Soundwise?
The main difference between 4 and 8
identical cores is resistance.
You get near half resistance (double conductivity) with 8 cores. Total section of that cable per signal is 28AWG (4 cores) and 25AWG (8 cores). 135mΩ (8 cores) vs 255mΩ (8 cores).
Guess there is no need to explain why lower resistance is much preferable (read the introduction at my list).
You should always keep output impedance (source + cable) the lowest possible as a norm, for electrical damping, efficiency and lower attenuation, etc.
It can be very important when dealing with IEMs equipped with balanced armatures, and/or low impedance. Of course, if your source output impedance is much higher than the difference of resistance between cables, 4 vs 8 cores becomes irrelevant for this purpose.
Other than this, you shouldn't notice much sound difference. I think you preserve better fuller bass with 8 cores version, but it could be bias; very slight difference, anyway.
Another thing to consider in this case, is you can mix both wire materials for each contact/signal (full mix) in 8 cores version. While in 4 cores version, positive signals will use one material, and negative (balanced) or ground (single-ended) the other. I don't think there will be audible differences between 8 cores and 4 cores version, if balanced. Guess differences when single-ended should be more noticeable, but haven't tested this yet.
I'd say, if you decide to invest in such quality cable, go for 8 cores if you can afford it, and forget future doubts. You'll get top notch cable for long, ultra versatile thanks to lower resistance, best wires combination, and usability with many IEMs and headphones thanks to adapters.
But you also can decide to invest less money with 4 cores version. It will be surely your best cable anyways, and you'll get the pleasure to taste this excellent cable.