We know the names of two more actors from the Fallout: New Vegas voiceover cast. They are Mitch Lewis, who voices a Caesar's Legion character known as Legate Lanius, and Marc Graue, who portrays the generic super mutants (you can hear samples of his prior work here).
Aside from being a voice actor, Marc Graue also runs the Marc Graue Voiceover Studios. It's now been confirmed that this is where Fallout: New Vegas voiceovers have been recorded. The same studio was previously used for recording the Fallout 2 and Fallout: Brotherhood of Steel voices (and their website design still looks like something from Fallout 2 days).