Atomoxetine is a NRI, it's not a SRI antidepressant, not a clinically significant one anyway... what made you think it has erectile dysfunction as a general side effect?

Phenylpiracetam might have a mechanism though very modest if at all - NDRI - that could benefit people with ADD. Piracetam is just a low potency glutamatergic drug with cholinergic properties. It's of no use for ADD treatment...

If you have ADD and severe enough to impact everyday quality of life, a supplement or nootropic won't do much of anything, this is a neurological disorder, such usually require treatments. You have a medication approved for it, i'd suggest giving it a chance. Most people usually wish to avoid stimulants as they fear they may impede their faculties in the long run, or become addicts, or damage their health, or <combination>... this medication will do none of these, or shouldn't. Likely won't find a nootropic to replace a treatment, be it stimulant or otherwise...