Hi Greeny
Please do not take the following as dismissive.
Seems to me that you are in the process of building a system and are asking questions to usual Hi-Fi shops. I would suggest you to not listen to anything they say from that point on. Define a budget. Discuss it with the people here, with us.
In the meantime do know the following:
Cables have no sound, should not have any ... There are several brands that build/sell excellent cables (Interconnects, USB, Speakers, yes! Power cables too) .. They do not need to be expensive. Two brands comes to mind.
Blue Jeans Cable and
Ghent Audio. Those people make excellent cables. I would lean on Blue Jeans if you live in the US.
As for the Electronics... Thanks to the tests and reviews of Amir, we know that $200 can give you a headphone system capable of driving any headphones on the planet to dangerous level with vanishing level of distortion. Affectionately known here as the ASR SPecial., this combo of the Khadas Audio Tone Board ($100) + The JDS Lab Atom headphone amp ($100) rivals in performance anything ou there, drive any headphones known to men, from the most sensitive to beasts such the HE6 and AKG K1000 with aplomb. Same amp dues to low noise drive sensitive IEM as well...
Speakers/transducers are where you spend your money. Depending on your room and tastes, think about adding 2 or more subs... Difficult to pull off but well worth it. For headphones .. Same: do not overspend ... in my new book,
$500 is the limit .. Think cans like Sennheiser HD650 or my personal favorite HifiMan HE560 ... There are many others. One of the best websites on the subject is from a person who post here: Solderdude...
https://diyaudioheaven.wordpress.com/headphones/recommended-ones/
Stay, ask questions. The answers here, more than, any other Audio enthusiasts sites, are deeply rooted in science and/or technology, a few opinions for sure but not wild things.
Peace and Welcome!