I used C4 for 2 months its great stuff, but i believe your body gets used to it after awhile and jumped to NO Explode and it helped get some of the intensity back. I have been out of gym for 8 mnths now and it pains me to try to start again after such a long layoff.
I really liked Usp Jacked 3d, the downfall was it made my stomach a litle upset and found myself doing the boot scoot to to bathroom mid workout. Also for a post workout you might want to try something called After Glow, its a little pricy, but helped out a lot.