Not to ask the obvious: but you did tell your AVR that no center was attached?
Though there's a healthy debate about localization: I can't think of any reason 2.0 would make voices hard to hear (other than an AVR thinking that there was a center and so not sending dialog to the L/R units).
As to what would be acceptable: since you already have the PSBs, I cannot imagine any reason you wouldn't plug them in and find out what you think (just make sure to re-enable center)