I have tested ECA (25mg Ephedrine, 200mg caffeine, 80mg aspirin) with a few of the products you mentioned. I have read that chromium isn't needed at all, pretty sure it was declared a bunk supplement. Now on the other hand I love to take 500mg of green tea extract (standardized for 50% ECGC) with every dose of ECA (take a dose of vitamin C with it, it helps the effectiveness of green tea). Yohimbine is also great, I take 15mg every morning before I eat and during morning cardio, but its best used when you have an empty stomach, something about carbs in blood renders it less effective. Thus I have a hard time taking it the rest of the day.
Now again I am not 100% positive on the broscience of this (broscience is a term used for theoretical meat head science often used on forums for bodybuilding) but...
ECA is great for burning off fat
green tea is great for burning off belly fat and depot fat
yohimbine is great for burning off depot fat.