Agree with the suggestion of the Ultradynamico Rose`. I've been running a set of the race series for a few hundred miles of gravel, love them so far. They were excellent in a race that featured about 50% mmr roads, and the rest were loose/sandy/deep. Was glad I had them on the front, but kind of wished I'd run them on the rear too....perhaps I would have had better traction on the rear if I'd gone with a little lower psi on the cave` I was running there.
I've also been happy running the RH Hurricanes. Plenty of traction, no real issues when running the standard casing. If not a lot of bite needed, but wanting extra cush, I thought the WTB horizon's I initially ran (in 650 x 47) were very plush, and rolled nicely on pavement. Not a ton of help when I was riding in loose/sandy, though I didn't ever completely washout, so perhaps that little bit of file tread on the sides was indeed functional.