| Check out Call of Cthulhu d20... It's extremely lightweight, although still d20. It's basically class-less; there are still feats and skills, but that's about it. It's similar enough to 3.x that the system really just disappears if your players already know how d20 games work. I can even send over some of my house-rules if you'd like, put together from a few years' experience running it.
While you might want to avoid the Sanity stuff for the kind of game you're looking for, it's got enormous sections on how to run a modern-day horror game. You could use the monsters pretty easily, too.
Psychic abilities are handled through feats. Their use drains Sanity and deals ability score damage. They aren't insanely flashy; the beefiest one is psychokinesis.
Spells, too, cost Sanity and ability score damage. They tend to be less flashy, but still quite powerful.
I think you could easily make it work, especially because 3.0/3.5 monsters are 100% compatible; I've pulled in giant scorpions just recently, as a substitute for eurypterids.
-O | 
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