I am not much of a fan of supplements especially any that are man-made. I am a strong proponent of whole foods with no or as little processing as possible.
I must admit that I do not know much at all about “C4 Extreme” and have never used it. Based on its use of Creatine and then “fusing” that to Nitrate, in my opinion you are simply throwing things in that do not have positive long-term benefits.
Everyone should keep in mind that the supplement industry is void of almost any level of regulation and as such it should NEVER be assumed that any particular supplement is safe or does what it claims. Read the disclaimers: that is how they stay in business and out of prison.
And even when they are able to do what they claim, they are regularly processed in facilities that also process many other products and there is no regulation to ensure that there is no contamination.
A good diet and good rest will provide you with what you need to get in a great workout without putting undue stress on your body. There is no magic bullet to a great workout. In fact, some supplements may tax your body because of inappropriate levels of nutrients that need to be cleared out.
Most of the people that take these supplements would actually get the same or better benefits by simply drinking 1 oz of water (please, not all from plastic water bottles) for every 2 pounds of body weight and avoiding caffeine. This amount of water is, for most people, enough to keep their bodies clear of build-ups that cause muscle pain and soreness. Proper hydration also allows you to workout more consistently with higher intensity.