For what it's worth, I managed to completely miss the fact that Bowers is black.
A few of my own thoughts:
Shar-- Vincent Kartheiser. Pretty. Somewhat effeminate. Capable of great angst (he did Whedon, for godssakes).
Councillor zh'Thane -- Stockard Channing. I have a whole new respect for her since she's been on The West Wing.
Treir -- Suzie Plakson. Duh.
Taran'atar -- Christopher Judge. The character has a Teal'c quality already, and Judge's voice would help fill the void left by Avery Brook's rumbling bass.
Vedek Yevir -- Ed Wasser. No one can play as slimy as Mr. Morden.
Bowers: J. August Richards. Not sure why, seems to fit.