Where to purchase cables?

I suggest you investigate Analysis Plus. They make cables for audiophiles as well as NASA and other reputable organizations. They rarely advertise because they reputation precedes them and they thrive on referrals. They are not pricing cables compared to many companies that do advertise as esoteric cables, but they are outstanding. After a customary break-in. I believe you will find they are musically excellent

I'm another who utilizes the Cable Company.

It’s become my default approach.

I've found someone there I trust and I always work with him.

Thank you all again for your thoughtful suggestions!

What have you ended up with? Or are you still searching cables?

The lowest price to performance ratio is from on-line cable makers keeping down costs by not charging and passing along dealer and distributor markups. 
Sometimes you can find top quality gear from small custom shops who do not do much advertising - costs which are passed to the buyer.
One interconnect maker of pure silver cables which makes some of the best money can buy - and they are not crazy expensive is at
silversolids.com