A 55 gallon would be the minimum size. The snowflake moray will eat anything that fits in its mouth, but the toby puffer, or blue-spot puffer, is known to co-inhabit with smaller fish like damsels. At the most, the eel, the puffer, and three damsel fish, IMO.
Are you sure an aggressive tank is the way you want to go? The novelty of flesh-eating fish wears off surprisingly quickly. I researched an aggressive set-up with a snowflake and a dwarf lion fish last spring but decided a reef tank was ultimately the way to go. You'll never get bored of that.
If and when you get those fish, add one at a time and make sure the tank is cycled well... at least three months. Get the damsels first to help seed things before the more expensive residents arrive.
Does this sound good to everyone else?