Where to purchase cables?

I bought my 4-conductor 12 awg OFC bulk speaker wire from Monoprice, and DIYed them.  Amazing bang for the buck.

Cables I get almost anywhere - custom made local guy, Amazon, Audiomart, Ebay, AliExpress, Craigslist, FB Marketplace, Reverb

For my main system I tend to purchase from my dealers. They will let me audition, but most are Transparent and I have most recently upgraded to the most recent. I usually keep old interconnects and use on my secondary systems. Upgrade your main system and use old ones on.
 

But for a secondary system I would go to the Cable Company… you can get used for half price. You can try also from their lending library. I am not a fan of most of the budget brand… I have found most to be no better than what comes with the component or you get at Best Buy.

I think you are requiring the assistance of a dealer. 

Or if you are going to go it on your own, since you posted here in Audiogon you might as well browse the cables ads. 

I've been extremely happy with my Pinetree Audio cables/speaker cables Excellent quality for the money and a pleasure to look at 

I’ve done a fair amount of a/b testing with Zu and 12 gauge cable.  I personally feel cables are complete ripoff’s. But there are audible differences.  They let you try them for two months for free. 
 

 www.zuaudio.com