Reborn's Anime's Cast
Don't ask me who they are, don't ask me who they are, don't ask me who they are.

Reborn リボーン： ニーコ （モデル）  <- Model
Tsuna ツナ： 國分優香里 （新人声優）  <- Newbie seiyuu
Goku 獄寺： 市瀬秀和（俳優）  <- Theatrical actor
Yamamoto 山本： 井上優 （舞台役者） <- Theatrical actor
Baby Ranbo 子供ランボ： 竹内順子 （声優） <- Naruto
Hibari 恭弥： 近藤隆 （若手声優） <- Train (Black Cat)
Kyouko 京子： 稲村優奈 （声優＆女優） <- Seiyuu + Actress
Haru ハル： 吉田仁美 （舞台役者） <- Theatrical actor
Iipin イーピン： チャン・リーメイ （日本と台湾のハーフ、舞台役者） <- Taiwanese & Japanese Half (so can really speak Chinese)
Adult Ranbo 大人ランボ： 津田健次郎 （声優） <- Kaiba (Yugioh), Inui (TeniPuri)
Ryouhei 了平： 木内秀信 （声優） <- Oshitari (TenPuri)
Bianki ビアンキ： 田中理恵 （声優） <- Chii (Chobitsu), Suigintou (Rozen Maiden)
Tsuna's Mother ツナ母： 深見梨加 （声優）<- Sailor Venus (Sailor Moon)

Okay, heard some of the sample voices.  Tsuna's voice is not bad (she was in Mushishi 2) but it wasn't a shouting voice.  At least sounds okay.
Goku's voice....10,000 miles from my imagination ^__^;; but let's see ... maybe his normal speaking is different from acting.
Yamamoto is also in Mushishi and sounds okay to me as well! (whew)
Reborn ... kinda weird voice... more like Boogie than Reborn but maybe that's not the voice used for Reborn.
Seems like Tsuna & Yamamoto are close to my imagination... but Goku T____T...hope the acting voice is different ... PLEASE.
The rest is fine but the rest HARDLY speak much (except baby Ranbo) and I have zero interest in the girls...