I have found that testing speaker cable is very hard if you have to shut down the system and swap cables to make the comparison. By the time you get it powered back up you have forgotten what the original set up sounded like. The best test that I have found is to use a stereo system that has a stereo/mono selector, you can test in the mono mode so that both channels have the exact same signal sent to the speakers. Put the speakers on both sides of the person who wants to make the comparison facing directly at them, make sure that they are equal distances from the listener. Connect the "good" cable to one speaker and the "cheap" cable on the other speaker. With the system set to mono you can instantly fade back and fourth between both cables using the balance control. I have found this to be a very accurate way to compare any cable.
As far as 16-gauge cable, I think that you are running on the thin side. If your amp has a very high current output you may notice a huge difference by using heavy gauge speaker cables. If you have a moderate power output and tend not to drive the speakers hard you may never know the difference.
The best demo that I have ever done was with my Parasound HCA 2003a amp, M80Ti speakers and a pile of different speaker cables. The Parasound amp is capable of insane output levels (300 watts @ 4 ohms and up to 60 amps of current per channel). I put the speakers about 15 feet apart faced at each other with me directly in the center, I tried everything from 24 gauge telephone wire to BI-wiring with Kimber 8-TC. The biggest difference was always noticed when I was playing music with deep bass passages at ear splitting levels. When I compared 18 gauge zip cord to the Kimber 8-TC it sounded like I added a very large powered sub to the system on the Kimber side, it was truly amazing. When I turned the volume down to reasonable levels the difference was still noticeable but not as dramatic. As long as I stayed above the 12 gauge thickness the difference between any of the cables was very small and more a matter of personal preference. I am not saying that there is not a difference between speaker cables, I just think that most of us can get by with any reasonable speaker cable that is of adequate size for the power levels you expect to achieve.
So with all of this said I would recommend 12 gauge or heavier speaker cable made from oxygen free copper having a high strand count (it just seems to bend easier and sound better). If money is not an issue I would suggest that you try some of the high-end speaker cables and see if you can find a difference.
Just my thoughts,