My relatively new boyfriend and I are heading up to San Francisco from L.A. next weekend for a wedding and we're having dinner Sat. night with another couple who are old, dear friends of his from New York. Since I've never met them, I'm channeling my nervousness into picking the "perfect" restaurant. I've done a little research and have reservations at Delfina, Kokkari and Two, and now I'm not sure which one we should go to. My prime concern is quality of food followed by atmosphere - it should feel cool and have a vibe, but not be too loud or trying too hard. Advice?