I originally purchased a cheap amp installation kit with a 4GA power cable for my new setup, thinking 4GA is 4GA and it doesn't matter who's name is on the jacket.
I decided to buy a second amp, so I bought a short piece of 8GA to run to each amp from a distribution block. I bought a few feet of a name brand power cable from a roll.
Eventually I opened up the amp kit and noticed the extra thick jacket on the power cable. Out of curiosity, I compared it to the name brand cable. This is a picture of the two, with the 8GA on the left, and cheap 4GA on the right:
As you can see, the 8GA wire is the same diameter as the cheap 4GA!
I went out again and bought 24 feet of brand name 4GA, and this is what it looks like compared to the cheap 4GA:
The jacket is the same diameter, but the cheap cable has half the wire! Note: the cheap cable does have 4GA written on the jacket.
Maybe I'm the only one surprised by this, and it could even be common knowledge, but I always thought there was no difference between cheap and expensive power cables. I mean, 4GA is 4GA. It's a measurement of the wire, not the jacket.
Anyway, lesson learned.