Do not mix two different downers with an upper. Benzos are more than safe alone with either Methylphenidate or amphetamine at reasonable (10-50 mg) and arguably due to being used for hospital stimulant overdoses, extreme doses of amphetamine are safe with a Benzo. Theres no telling what can happen to your body or brain, even death when a third compound is thrown into the mix. (Clonidine).
Rule of thumb: Some Combinations of two drugs (Amph & Benzo) are definitely safe, or definitely dangerous (Benzo & Opiate). But all combinations of three drugs can be devastatingly unpredictable.