Both Filia and Valgarv come to life with the help of their very talented seiyuu (Japanese voice actors). Here is some basic information on them that can be easily obtained anywhere. It's all I can find for now so if you have any added faqs please let me know. I was going to post some information about their English voice actors (Tara Jayne and Scottie Ray) but I can't find any sufficient information on them, especially on Scottie. (who I adore)

Kuwashima Houko

Kuwashima Houko debuted her career as Yurika in Nadesico, which gained her a fair amount of popularity, after that she was cast as Filia in Try which by then her popularity had sky-rocketed. She has a beautiful singing voice and has done several opening and ending theme songs. She is also a part of the music groups S-nery, S-nery V, and Girls Be. Right now I believe her last role was Nakahito in Steel Angel Kurumi. She was born on December 12th, 1975 in Iwate Japan and currently works for Aoni Production.

Some of Houko's anime roles...
Betterman - Asami Miyako
Detective Conan - Nanigawa Ayako
Dokkiri Doctor - Koizumi Miyuki
Gekigangar 3- Sapphire Misumaru Yurika
Gokudou-kun Man'yuuki - Koko-Hime
Kaitou Ranma - Sana
Kamikaze Kaitou Jeanne - Kusakabe Maron (Jeanne)
Kidou Tenshi Angelic Layer - Sai Jinouji
Koutetsu Tenshi Kurumi - Kagura Nakahito
Master Keaton - Sayuri
Mugen no Ryvius - Erina Rigubii
Nadesico - Misumaru Yurika
Noir - Yuumura Kirika
Slayers - Filia

Wataru Takagi

Takagi-san does the voice of the sexiest Slayers male of all time... Valgarv!! Takagi was born on July 25th, 1966 in Chiba, which is a district of Tokyo Japan. He currently works for Arts Vision and has done a wide variety of characters. He has proven his worth as a singer as well especially with Val-kun's image song, which has a heavy metal type feel. Sadly he has yet to release any solo albums. His last role to date was Onizuka from GTO but I am not positive. His debut was as an unknown character in the series Mr. Ajikko.

Some of Wataru's anime roles...
Armitage III - Lowell Guntz
Beast Wars - Cheetas
The New Cutey Honey - Hayami Akakabu
Dectective Conan - Genta
Dirty Pair Flash - Baran
Gundam X - Garold Ran
Iria: Zeiram the Animation - Zeiram, Nanbu
Koko ha Greenwood - Yanagisawa
Monster Farm - Suezo
Princess Rouge - Yuusuke
Sailormoon R - Rubeus
Slayers - Valgarv
Shin Tenchi Muyo! - Hotsuma
Tenchi Muyo! - Kamidake