I think the most important thing as far as voice acting is narration. Provided Project Eternity is the kind of game that will support narration (I hope so), I think this is far and away the best place you could put your voice acting budget. Bring back Kevin Michael Richardson!
That being said, I thoroughly enjoyed the level of voice acting done in games like BG, BG2 and P:T. Some important scenes and characters are voiced, as are emotive responses, but the majority of dialogue relied on text.