Name aside, I recommend thinking of it like the Monk's ki. We all agree Monks can use meditation and mental discipline to achieve supernatural effects, right? I mean, six of their class abilities are (Su). I'd think of psi the same way. Psions and Psychic Warriors (and to a limited extend, Wilders) all use meditation and mental discipline to achieve supernatural effects, just like the Monk does. As a result, they're no more "sci fi" than Monks are.
It can help, though, to strike all instances of the word "crystal" and replace it with "gem".