Well, I personally grabbed this from the Korean client - if there is a new champion coming out, I guess I can frequently update this thread. Decided to share it with everyone. xD
I also tried grabbing the Chinese one from the China client, but they are behind us a bit so the voices are not evenly matched with the champions.
Here is the download link to the Korean voice pack. I already renamed it to replace the English one. What you do is go to your Riot Games folder.
RADS->projects->lol_game_client_en_us->managedfiles->data->SOUNDS->FMOD->And replace VOBank_en_us.
That is it. ^^ The champions will now have a Korean voice in-game and the announcer is kind of creepy too. >.> But Jarvan's voice. <3
And Ahri, for you boys. xD