ZMA only helps test levels if youre deficent in zinc or magnesium, where as most people are not who eat...so it is worthless, tribulus is good if you need an increase in sex drive, won't help with much more than that though. 6-Oxo was designed as an estrogen blocker to use while on something else, or post cycle..a 6-oxo only cycle won't do much for you... 17-hd will give you a decent pre-workout boost but it's not much more than a few herbs thrown together. Amplify02 is great for pre-workout energy, pumps, strength, and some fat burning...
I've personally used 17-HD back when i was a supplement whore, but since then I've realized real food is the only legal supp that produces results...just eat a lot, rest, train hard and you will gain muscle. I've stopped whoring supps, just stuck with a lot of food, a multi, and a couple diff protein powders and have gotten the best results to date. However I did just order a bottle of amp02 as I got my best friend to guinea pig it last time, and he loved it so much that he convinced me to get some. I'll be posting a log of it, so you'll know what i think.