The first three Vanguard books are annotated (Harbinger, Summon The Thunder, Reap The Whirlwind), and assuming you read them in order they don't require any other novels to understand. Plus they're totally badass.
Section 31: Rogue stands alone, but it's not especially great as a novel. Not bad but not noteworthy.
Sword Of Damocles, the fourth Titan novel, also stands alone reasonably well. There aren't too many ongoing stories through the Titan novels. You mention Bennett, though, so there's a chance you've read Orion's Hounds (book 3) anyway. If you haven't read Titan at all, just start with Orion's Hounds; the first two are kind of a side-story, and book 3 gets the series really going.