I know that body building can become a sort of addiction, and you want to see results faster. Please remember that balance is important in all things. My boyfriend has read a lot about these supplements, and his brother is addicted to them. The brother has problematic mood swings and has trouble getting along with people. Not only that, but he admits they cause ED and shrinking of his genitals.
My boyfriend started taking this and that, and had his first experience with ED. He was horrified. It took about a week to get back to normal, and he was barely taking anything compared to his brother. Now he stays away from the stuff that tweaks testosterone.
What are you trying to accomplish? Get some exercise, or look a certain way? Unless you're a professional bodybuilder who will make a ton of money doing this, it's a bad idea for your health. Of course you're free to do what you want with your body, but as this is a nutrition forum, it's unlikely any of us will encourage you to overdo anything. Now, what are these downsides? Excess testosterone will cause premature enlarged prostate and possibly prostate cancer, as you'll have excess testosterone to oxidize. You might develop anger issues. Excess protein causes kidney disease. Now, some of the things you've mentioned are less harmful than others, but if you truly just want to be fit, do it by working out and eating right. If you truly want to get bigger than your natural state allows, then you need to look up the old Arnold Swartzenegger mags -- they'll even tell you how to get the real stuff and how to inject it if you really want to go that way. Made him rich, but also made him the troubled adult he is. Make your choice.