So I have this character and I can't choose which of these names I like the most. I'd just like opinions on which one is the nicest.

Mikhail
Nikolai or Nicolai
Sevastyan or Sevastian
Dmitry or Dmitri

He's a Russian living in Moscow and is in his early twenties. He's also living in a run-down apartment and plays the piano at bars for a living. He's quite poor, and he's trying to get out of Russia (keep in mind he's living in the 1930s). He managed to evade becoming a soldier and tries to stay out of trouble by avoiding conversations about the government as much as possible.

Currently, all he wants is a ticket to somewhere out of Russia and a Grand Piano. He tries half-heartedly to stay away from alcohol because, though it helps him escape, it does very strange things to his personality, which is usually a lovely puce color. Sarcastic, prickly, and cynical, of course. If you get to know him, you'd realize he's really a hopeless romantic and is extremely lonely, though he'd never admit it.

And his last name is Nosova.