Best way to buy speaker cables and to evaluate them

I realized I did not quite answer your question, and only gave a recommendation with an implied answer.  You will likely have to try a few brands before you find what you like, buying used is the most economical route, and as others have stated, be aware of the used market for what you buy with an eye towards reselling if you don’t like them. AZ is a good place to “start” and as it has a very active market and the price is approachable. 

I was not a "cable denier," but I was a bit skeptical of spending "lots" of money on cables.  I did figure that buying reputable cables in the lower mid-range would make a difference in the sound. I did spend on better speaker cables, however, including AQ Rocket 88, some custom Mogami's, and Raven Audio; they made some improvement, but nothing dramatic.  Then, I read a number of items about Silversmith Fidelium speaker cables and, learning that the owner, Jeffrey, offered a trial period, I gave them a go.  Well, both my non-audiophile (but music loving) wife and I were shocked when we hooked up the Fidelium speaker cables to the Odyssey Kismet (in Khartago cases) mono bloc amplifiers.  The improvement in sound quality--tonal character of instruments, sound stage, and the location of instruments and voices--was simply astounding.  I knew within a minute or two that the Fidelity's far surpassed anything else I had tried thus far.  

I then purchased a pair of Fidelium XLR interconnects to connect my Gungnir2 DAC to my Rogue Audio RP-7 preamp--replacing mid-grade Morrow interconnects, and while the improvement was nearly so dramatic, it was quite noticeable.  I also am using Ice Age Audio OFC power cords in my system.  While my system is probably mid-fi, I am quite pleased with the results.  

So, for me, the best way to buy cables is to find a company that offers a trial period and go that route; so far, there is nothing that I have had to send back.

"Get these shotgun bi-wire Acoustic Zen Satoris."

The AZ speaker cables are a solid recommendation by @soix.  I owned their Double Barrel cables that sounded very good in my system, and you could also look into their Hologram speaker cables.  

Another from the same era to consider are Harmonic Technology (Pro 9+ or Pro 11+) that are constructed using solid core OCC wire that is individually insulated with foamed PE.  As said by others, these previously well-regarded cables that can currently be purchased at budget prices are a good place to start to determine whether more expensive cables make a meaningful difference in your system to your ears.

@bigtwin 

Wow. My condolences. What a shame.

i didn’t realize it, until you mentioned the claims of the cable companies. I don’t think I have ever read them. Ever. I have always read reviews of cables and other things but never actually the color glossies probably also true with components.

@willywonka 

What I do lack is direct observation and comparisons between various cables in my system

Then The Cable Co. (or ordering from smaller companies that offer return policies) is clearly the way to go. BTW, the Cable Co. borrow charge is credited to any subsequent purchase.