What cable companies make the best cables and sell them directly?

Unfortunately, it depends. The cables you want are going to complement your system and move it in a direction that is positive for you. Which depends on your values in sound… as well as your system taken as a whole.

Finding these typically requires trying them out. Cardas are a tad warm and enhance most systems. Transparent are that. DHLabs has really good budget cables. The Cable company allows you to rent different kinds to try them.

Half price is typical for used.

Trying several kinds is probably most important.

OP,

I do have another recommendation. Do NOT make a decision based on the information on the manufacturer’s web site. I am not saying it is wrong… it is just not helpful in decision making. If it tells you all about their technology… it just doesn’t matter. It is what it sounds like in your system, with your components in your audio room.

I recommend reading reviews… from legitimate sources, Stereophile, The Absolute Sound, and HiFi+. Also, listen to some and see what they do in your system and compare with reviews. If your system is very modest… great interconnects may do nothing, if it is intermediate or high end it could be jaw dropping. I have spent hundreds of hours evaluating for my systems. I recently tried out a $7K cable from a very high end company… it sounded terrible… this is very uncommon, but can happen.

If your system is already leaning to be too detailed and trebly… a really good clear set of interconnects can tip it over it over into the fatiguing side. While warm ones would provide a heftier mare natural sound. Generally copper is warm, silver coated copper is warm with added details and silver is very detailed but can be harsh. But the design of a good cable can override the underlying material.