Soooooooo not that I want to get in the middle of another pissing match, but when talking about wire there is another thing to think about besides just OFC or CCA......your end terminations.
There's so much more to it then just copper or aluminum.
Soldered terminals, crimped, fuses, how many fuses, quality of solder, amount of solder, type of crimp...........
When you combine different metals there is also a voltage drop incorporated with that as well.
Copper terminals, aluminum terminals, plated terminals, surface area of contact....
Take that into account when you're discussing your real-world results as well.
There are literally thousands of combinations of equipment (besides the HU, amps and speakers) that make up your system and every little bit is going to affect it.
All those small voltage drops probably add up and account for more voltage drop then a huge span of OFC or CCA.
The way I look at it is this: Look at your system parameters and calculate the appropriate gear for the requirements. A great rule of thumb is 2x what you need for reliability.
Then if you're happy with your voltage drop and all, then great, you're DONE!
As was said above 99% of us aren't hard core competitors so gaining that 0.2V or 0.5dB isn't going to amount to squat on the Ear-O-Meter so just have fun with your system.