Well, after watching lots and lots of anime, I can somehow identify some of the voice actors (usually male CV):
Tomokazu Sugita: voiced Kyon in Melancholy of Suzumiya Haruhi
Tomokazu Seki: voiced Yuri in God save our king
Jun Fukuyama: voiced Lelouch in Code Geass
Ono Daisuke: voiced Koizumi in Melancholy of Suzumiya Haruhi
Hiroshi Kamiya: voiced Izaya in Durarara!!
Akira Ishida: voiced Athrun Zala in Gundam
Soichiro Hoshi: voiced Kira Yamato in Gandam
Midorikawa Hikaru: voiced Heero in Gumdam Wing
Among the female Seiyuu, I can identify Rie Kugimiya (voiced Shana in Shakugan no Shana, etc)
I can identify more but forget their names. I think Jun Fukuyama have at least three ranges of voice and he is my fav Seiyuu.
So, how many seiyuu can you guys identify?