Could you incorporate psi stuff from the psi handbooks into SA?
Are you talking about 3.0/3.5 psionics? If that's the case, then no, or at least not without a lot of adaptation. SA uses a "skills and feats" system similar to Force powers in Star Wars- entry level feats grant access to psionic powers in the form of skills. Since there arent' individual powers or levels, you couldn't really port those over directly.
You could probably allow access to various psionic feats if you wanted to (Up the Walls, etc), but I think that SA had most of those already covered. For that matter, their powers cover most of the sorts of things you'd do with 3rd ed psionics, provided it at least sort of fit in the modern world (ie no plane hopping, astral constructs, etc).
As for magic, the system's again feat based, though there aren't any skills to go with it. Instead, the feats allow you to use more and more powerful occult-style spells called rites or rituals. The trick is, you have to have followers to draw power from for these rituals, you can't cast them on your own (well, eventually a magician can get powerful enough to cast lesser spells on their own, but that's more in the province of "mad villain" NPCs).
So magic isn't really something the PCs can fling around at whim- that's why the psionic classes are in SFA, to give them access to FX. It's set up so that the psionic classes will get most of the access to powers, but other characters might be able to spend a feat or two to get minor abilities, depending on how the GM wants to do things. Oh, there's also various occult prestige classes that revolve around the use of relics, spells, etc. The only one in the SFA book is the Shadepseaker, a sort of mystic assassin who communes with the dead.
Hope that helps. A couple of other notes- SFA has been cancelled, and there's supposed to be a new version of Spycraft coming out sometime, maybe later this year. So maybe that will change your decision, maybe it wont. At any rate, I'd say that you would definately need the Spycraft book to make sense of most of the SFA rules.
