Speaker Cables

One of the problems is that different people appreciate different sound. Also, the overall sound you get is the result of all the components together. For quit a while in my early days I bought some very high quality interconnects and speaker cables and they made my system sound terrible ... too harsh and trebly. Those were Transparent Audio. It wasn’t the interconnects, it was my system. Years later after several upgrades I pulled out my old Transparent and they were wonderful. All my interconnects are now Transparent Ultra Gen 5. They are... well, transparent. So, you have consider the overall sound of all of your equipment and speakers together when making a choice. If you want to hear what your system sounds like, I highly recommend Transparent. I believe they are second highest selling high end after WireWorld. There is really good reasons to stick with the big brands... Audio Quest is the third. Ample reviews, proven record, resale value... tested value to cost ratio.
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Now is when someone will chime in and say, you shouldn’t use your interconnects as balance control... well, yeah but sometimes you have what you have and you can’t drop $100 grand to make the signal perfect. All copper tends to warm the system... is safe, all silver brings out details but your signal better not be harsh, or you are going to hear it! Silver coated copper can be ideal... if this sounds harsh to you, you have a real system problem! Do not... DO NOT... make a decision on cables or interconnects before you have a couple hundred hours of play on them... I have a cheap little system just to break stuff in.
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My experience is bi wiring isn’t a big enough factor to be worth it. Biamping only if you really love futzing with really complex problems with multiple variables after you have your ideal system. If all your components are not great, then don’t screw around with it... unless you think it is fun.

One of my favorites, which I still use on my office system was HD12D... something like that. Years ago, I think it was Stereophile or The Absolute Sound, just for fun, went to Home Depot and got a 12 gauge extension cord and threw it into the mix. It was actually really good. So, for my let's see... $5 or 6K system crammed in my office it is great. But for my main system with Sonus Faber Amati Traditional speakers and All Audio Research Reference stuff, it doesn't cut it. 

@cakyolFor your main system, go up to 6 AWG then :-)At that thickness, almost all copper wires will have negligible resistance.Seriously, as I said, check the inductance and capacitance of the wire and buy accordingly :-)I 
I find my Transparent Ultra cables significantly better in my main system. While I have not tried 6 AWG I feel I can trust the engineers at Transparent to have considered it.

My observation was that the Home Depot wire is better than the spools of... what was it 20 gauge? 22 gauge? Two conductor wire that was the only readily available wire 30 years ago. Generally good to hook up a system that wasn’t likely to improve much with a high end wire choice.