hell yeah man, Amp-C i know is polarizing because some dudes love it, and others have said they are off of it, and not as good as DMAA, so youll have to be the judge there, but Id be surprised if you were dissapointed.
As far as centurion, they are just still small and up and coming. Ive met there CEO recently they are a great bunch of people, and I would put them in the PES / SNS / Evomuse / CL category of companies who work hard, are honest, and are trying to go right by the consumer (as much as the industry allows) but also have earned at least my trust, and are growing. They fairly recently signed Guy Cisternino as their premier athlete, and face of the company. Whats cool though, he is more like a member of their team as much as the young guy that packs boxes at the warehouse for shipping hes really into it, not like some companies where the sponsorship is really just a meal ticket. Also, knows anything about Guy himself, he is one of the coolest, hardest working guys in the IFBB, and a guy that you can feel good about being a fan of. Just my opinion about stuff.