HOLY GOODNESS. Daario Naharis was not in his twenties, you know.
Odad Fehr seems like a decent Daario (just googled it)
Or the guy who played Sibylla's husband in Kingdom of Heaven (OMFG, that was Marton Csokas???????? OMFG. Okay, I still stick with the Daario theory, just omfg... that guy is from my country. No, but he's a citizen of my country according to imdb) - Though, he would make a fine Mance Rayder too...
Erm... the guy... who played Alex Kingston's lover in that horrid movie about Boudica ( Hugo Speer, Imdb is my friend)
The guy who played Gaston in the movie about D'Artagnan's daughter... Casper Zafer.
But even more so... Marcus Jean Pirae who played Captain Villeroi in the very same movie.

Hi

Thanks for the comment. Where did you get the idea that Daario is not in his twenties? Just want to re-read.
To be honest it has been a while. In my head he is somewhere between 23-35. I have to admit that I did not check the actors ages and instead went for their cheeky, sexy looks.

Have now checked their ages and am myself surprised at the range;
Sergio Muniz is 37
Max Befort is 23
Dustin Clare is 30
Charlie Hunnam is 32
Gilles Marini is 36
Gaspard Ulliel is 27
Rodrigo Santoro is 36
Guilio Berutti is 27
Dudley is 22
and Michael Ealy is 39, the golden oldy I suppose.

No idea who he is but he has the right look. Dark and sexy.
OR Ben Barnes or Aidan Turner. Santiago Cabrera would work too.

Er... I remember some statement about him being middle aged, but it may just happen, I only imagined it. I always pictured him around 40. That probably has a lot to do with my own taste which prefers man between 30-50. Yes, I'm sick XD
Anyway the ages are interesting... I guessed them between 20 and 30 pushing to early thirties. Surprising. :)