Based on my own experiences, admittedly, I'd suggest going a bit bigger than a 14 gallon. If we're talking about a biocube (my assumption since I've not heard of the Biodome before) you might consider going for a 29, or just build a tank up from scratch (So to speak.)
I started with a 37 which cycled and was running with fish in less than a month (Believe it or not, it has been stable since), and a five I meant to use as a semi-display quarantine (Which took FOUR months and several modifications to stabalize). even more than fresh water, Saltwater lives with the more water equals more safety.
That being said, if your confident of your abilities with the water chemistry, go for the fourteen. Just know you're going to have to watch it, and even among the nano-fish you're pushing it with more than two small fish, right out of the gate.
Also be aware, if you might ever go reef (And again, I've discovered it's hard not to. Especially since my LFS
has a guy who's like a coral crack dealer. Seriously) you'll have to consider the fish based on if their reef safe, though to be fair most of the nano's I've looked at really are.. but that might just be I somehow draw myself right to the fish.
As for starfish, they'll (Most at least) eat anything that moves slow enough. Including small fish and corals.
Lastly, don't waste the money on live sand. Live rock is worth the money, live sand isn't really quite "Alive" enough, and any sand will be "live" in a very short time once in the tank.