While I did watch Hanasaku Iroha in the search for something similar to Hyouka, it wasn't what I got. Though I did enjoy Hanasuka Iroha immensely for its great characters, the character interactions, the tiny bit of romance and some of the drama (felt like melo/forced-drama at points), I really didn't get the Hyouka feel.

I would strongly recommend SNAFU (or Yahari Ore no Seishun Love Comedy wa Machigatteiru.). The premise is sorta the same; you have your introverted, pessimistic male MC that is forced into club, though here it's the Volunteers Club aimed at helping students with personal and social issues.

I will start by saying that you won't find any real romance in this show (though that may change with the upcoming second season this spring!) but they do talk about romance in a form of social-commentary. Actually, this entire show could be summarized as a form of social commentary!

The similarity to Hyouka is its strong cast of characters and how they interact. You will also find A LOT of similarities between the MCs, though Hachiman in SNAFU is more of a pessimist than Oreki, but they are both very poetic and idealistic about their thoughts and opinions regarding humans and society as a whole. You will also find Hachiman going into long monologues like when Oreki tries to solve a mystery. The side-cast are good (some of them very good) and varied but not as focused on as Hachiman (like Hyouka, the show is told from the MCs perspective)

Regarding visuals and music they are MILES AWAY from the amazing quality of Hyouka. Though it's not bad, IMO they're just good, above average. That concludes pretty much what I got to say about it.

You might also want to check out Gosick. I recently picked this one up (only watched one ep!) but it premise sounds interesting. Set in 20th century Europe, a boy and a girl end up traveling around Europe solving mysteries while also developing a relationship. So far I'm not completely sold on the characters and the tone of the series, but I'll continue watching.