I've been to all three in question.
N9ne is the best of the bunch. The food is great, but it is a steakhouse. We had stone crabs and shrimp cockail w/ a bottle of Vilmart & Cie NV, then when each had Surf and Turf (a petite filet and half a lobster, it was a special) with a bottle of Justin Isocoles(sp) '01. A side of mashed & a side of broc. The food was great, the service was excellent (i managed to spill my whole water glass n my fiance's dinner, which was deftly resolved). A fab experience, but pricey.
Sushisamba and Narcisse are about the same in quality but with very different feel. Sushi feels very chainy and Narcisse more than feels like a bar. I wold go back to Sushi of the two.
Sushisamba: Had Tuna ceviche, GREAT! Fiance had the crab cake, which she thought was great, and she is a crabcake vertran. Had a Arrowwood Chard '01, the were out of the wine i wanted, buy i really likd this one. We got suckered into sushi, we had two pieces of otoro-not so good, i wouldn't order sushi. She had the ribeye, i had the snapper. The snapper was good, but the steak was great. We had a pinot from new zealand, but the name escapes me. Good exp, fun atm (i sent some out of town business associates who loved it). i would retutn.
Narcisse, went for a post v-day celebration. Had the tasting...don't remember the app, a cesar salad, a tuna steak, and a great dessert. Drank some Veuve gold label. the food was good, the portions weren't sized down for the tasting, but nothing was spectacular. This was the most expensive dinner we've ever bought - we've done some pretty swanky places tru, everest, ambria, spiaggia (all of which i thought provided good value for the cost) - and i didn't think it lived up to the cost.
Just my 2 cents