TV Tokyo, the station that will broadcast the upcoming anime Sonic X this April has updated their Sonic X section of the site with tons of new info including the Japanese voice cast and profiles of the characters.
The main site is here: www.tv-tokyo.co.jp/anime/sonic_x/main_index.html
Japanese voice cast here: www.tv-tokyo.co.jp/anime/sonic_x/staff_cast.html
Character profiles here: www.tv-tokyo.co.jp/anime/sonic_x/character.html
More info can be found at the site.