Phenylpiracetam builds tolerance FAST. There are a couple vendors who sell the bulk powder cheap, but I'm not sure if it's appropriate to mention them here. Easy to find though on Google. It's an immediate, stimulant-like, clean feeling. That goes away very quickly with repeated use though.
Sunifiram was okay, I seemed to have got a mild mood lift and some clarity, but nothing dramatic. Some report dramatic results, and not really any tolerance issues